Snippets Archive
These snippets, while useful and interesting, didn't quite make it into the repository due to either having very specific use-cases or being outdated. However we felt like they might still be useful to some readers, so here they are.
Table of Contents
JSONToDate.mdspeechSynthesis.mdbinarySearch.mdcollatz.mdcountVowels.mdfactors.mdfibonacciCountUntilNum.mdfibonacciUntilNum.mdREADME.mdhttpDelete.mdhttpPut.mdisArmstrongNumber.mdquickSort.mdremoveVowels.mdsolveRPN.mdhowManyTimes.md
JSONToDate
Converts a JSON object to a date.
Use Date(), to convert dates in JSON format to readable format (dd/mm/yyyy).
const JSONToDate = arr => {
const dt = new Date(parseInt(arr.toString().substr(6)));
return `${dt.getDate()}/${dt.getMonth() + 1}/${dt.getFullYear()}`;
};
Examples
JSONToDate(/Date(1489525200000)/); // "14/3/2017"
speechSynthesis
Performs speech synthesis (experimental).
Use SpeechSynthesisUtterance.voice and window.speechSynthesis.getVoices() to convert a message to speech.
Use window.speechSynthesis.speak() to play the message.
Learn more about the SpeechSynthesisUtterance interface of the Web Speech API.
const speechSynthesis = message => {
const msg = new SpeechSynthesisUtterance(message);
msg.voice = window.speechSynthesis.getVoices()[0];
window.speechSynthesis.speak(msg);
};
Examples
speechSynthesis('Hello, World'); // // plays the message
binarySearch
Use recursion. Similar to Array.indexOf() that finds the index of a value within an array.
The difference being this operation only works with sorted arrays which offers a major performance boost due to it's logarithmic nature when compared to a linear search or Array.indexOf().
Search a sorted array by repeatedly dividing the search interval in half.
Begin with an interval covering the whole array.
If the value of the search is less than the item in the middle of the interval, recurse into the lower half. Otherwise recurse into the upper half.
Repeatedly recurse until the value is found which is the mid or you've recursed to a point that is greater than the length which means the value doesn't exist and return -1.
const binarySearch = (arr, val, start = 0, end = arr.length - 1) => {
if (start > end) return -1;
const mid = Math.floor((start + end) / 2);
if (arr[mid] > val) return binarySearch(arr, val, start, mid - 1);
if (arr[mid] < val) return binarySearch(arr, val, mid + 1, end);
return mid;
}
Examples
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 6); // 2
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 21); // -1
collatz
Applies the Collatz algorithm.
If n is even, return n/2. Otherwise, return 3n+1.
const collatz = n => (n % 2 == 0 ? n / 2 : 3 * n + 1);
Examples
collatz(8); // 4
countVowels
Retuns number of vowels in provided string.
Use a regular expression to count the number of vowels (A, E, I, O, U) in a string.
const countVowels = str => (str.match(/[aeiou]/gi) || []).length;
Examples
countVowels('foobar'); // 3
countVowels('gym'); // 0
factors
Returns the array of factors of the given num.
If the second argument is set to true returns only the prime factors of num.
If num is 1 or 0 returns an empty array.
If num is less than 0 returns all the factors of -int together with their additive inverses.
Use Array.from(), Array.map() and Array.filter() to find all the factors of num.
If given num is negative, use Array.reduce() to add the additive inverses to the array.
Return all results if primes is false, else determine and return only the prime factors using isPrime and Array.filter().
Omit the second argument, primes, to return prime and non-prime factors by default.
Note:- Negative numbers are not considered prime.
const factors = (num, primes = false) => {
const isPrime = num => {
const boundary = Math.floor(Math.sqrt(num));
for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
return num >= 2;
};
const isNeg = num < 0;
num = isNeg ? -num : num;
let array = Array.from({ length: num - 1 })
.map((val, i) => (num % (i + 2) === 0 ? i + 2 : false))
.filter(val => val);
if (isNeg)
array = array.reduce((acc, val) => {
acc.push(val);
acc.push(-val);
return acc;
}, []);
return primes ? array.filter(isPrime) : array;
};
Examples
factors(12); // [2,3,4,6,12]
factors(12, true); // [2,3]
factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12]
factors(-12, true); // [2,3]
fibonacciCountUntilNum
Returns the number of fibonnacci numbers up to num(0 and num inclusive).
Use a mathematical formula to calculate the number of fibonacci numbers until num.
const fibonacciCountUntilNum = num =>
Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
Examples
fibonacciCountUntilNum(10); // 7
fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1).
Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two.
Uses a mathematical formula to calculate the length of the array required.
const fibonacciUntilNum = num => {
let n = Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
return Array.from({ length: n }).reduce(
(acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
[]
);
};
Examples
fibonacciUntilNum(10); // [ 0, 1, 1, 2, 3, 5, 8 ]
Snippets Archive
These snippets, while useful and interesting, didn't quite make it into the repository due to either having very specific use-cases or being outdated. However we felt like they might still be useful to some readers, so here they are.
Table of Contents
JSONToDate.mdspeechSynthesis.mdbinarySearch.mdcollatz.mdcountVowels.mdfactors.mdfibonacciCountUntilNum.mdREADME.mdhowManyTimes.mdisArmstrongNumber.mdquickSort.mdremoveVowels.mdsolveRPN.mdfibonacciUntilNum.md
JSONToDate
Converts a JSON object to a date.
Use Date(), to convert dates in JSON format to readable format (dd/mm/yyyy).
const JSONToDate = arr => {
const dt = new Date(parseInt(arr.toString().substr(6)));
return `${dt.getDate()}/${dt.getMonth() + 1}/${dt.getFullYear()}`;
};
Examples
JSONToDate(/Date(1489525200000)/); // "14/3/2017"
speechSynthesis
Performs speech synthesis (experimental).
Use SpeechSynthesisUtterance.voice and window.speechSynthesis.getVoices() to convert a message to speech.
Use window.speechSynthesis.speak() to play the message.
Learn more about the SpeechSynthesisUtterance interface of the Web Speech API.
const speechSynthesis = message => {
const msg = new SpeechSynthesisUtterance(message);
msg.voice = window.speechSynthesis.getVoices()[0];
window.speechSynthesis.speak(msg);
};
Examples
speechSynthesis('Hello, World'); // // plays the message
binarySearch
Use recursion. Similar to Array.indexOf() that finds the index of a value within an array.
The difference being this operation only works with sorted arrays which offers a major performance boost due to it's logarithmic nature when compared to a linear search or Array.indexOf().
Search a sorted array by repeatedly dividing the search interval in half.
Begin with an interval covering the whole array.
If the value of the search is less than the item in the middle of the interval, recurse into the lower half. Otherwise recurse into the upper half.
Repeatedly recurse until the value is found which is the mid or you've recursed to a point that is greater than the length which means the value doesn't exist and return -1.
const binarySearch = (arr, val, start = 0, end = arr.length - 1) => {
if (start > end) return -1;
const mid = Math.floor((start + end) / 2);
if (arr[mid] > val) return binarySearch(arr, val, start, mid - 1);
if (arr[mid] < val) return binarySearch(arr, val, mid + 1, end);
return mid;
}
Examples
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 6); // 2
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 21); // -1
collatz
Applies the Collatz algorithm.
If n is even, return n/2. Otherwise, return 3n+1.
const collatz = n => (n % 2 == 0 ? n / 2 : 3 * n + 1);
Examples
collatz(8); // 4
countVowels
Retuns number of vowels in provided string.
Use a regular expression to count the number of vowels (A, E, I, O, U) in a string.
const countVowels = str => (str.match(/[aeiou]/gi) || []).length;
Examples
countVowels('foobar'); // 3
countVowels('gym'); // 0
factors
Returns the array of factors of the given num.
If the second argument is set to true returns only the prime factors of num.
If num is 1 or 0 returns an empty array.
If num is less than 0 returns all the factors of -int together with their additive inverses.
Use Array.from(), Array.map() and Array.filter() to find all the factors of num.
If given num is negative, use Array.reduce() to add the additive inverses to the array.
Return all results if primes is false, else determine and return only the prime factors using isPrime and Array.filter().
Omit the second argument, primes, to return prime and non-prime factors by default.
Note:- Negative numbers are not considered prime.
const factors = (num, primes = false) => {
const isPrime = num => {
const boundary = Math.floor(Math.sqrt(num));
for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
return num >= 2;
};
const isNeg = num < 0;
num = isNeg ? -num : num;
let array = Array.from({ length: num - 1 })
.map((val, i) => (num % (i + 2) === 0 ? i + 2 : false))
.filter(val => val);
if (isNeg)
array = array.reduce((acc, val) => {
acc.push(val);
acc.push(-val);
return acc;
}, []);
return primes ? array.filter(isPrime) : array;
};
Examples
factors(12); // [2,3,4,6,12]
factors(12, true); // [2,3]
factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12]
factors(-12, true); // [2,3]
fibonacciCountUntilNum
Returns the number of fibonnacci numbers up to num(0 and num inclusive).
Use a mathematical formula to calculate the number of fibonacci numbers until num.
const fibonacciCountUntilNum = num =>
Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
Examples
fibonacciCountUntilNum(10); // 7
Snippets Archive
These snippets, while useful and interesting, didn't quite make it into the repository due to either having very specific use-cases or being outdated. However we felt like they might still be useful to some readers, so here they are.
Table of Contents
JSONToDate.mdspeechSynthesis.mdbinarySearch.mdcollatz.mdcountVowels.mdfactors.mdfibonacciCountUntilNum.mdREADME.mdhowManyTimes.mdisArmstrongNumber.mdquickSort.mdremoveVowels.mdsolveRPN.mdfibonacciUntilNum.md
JSONToDate
Converts a JSON object to a date.
Use Date(), to convert dates in JSON format to readable format (dd/mm/yyyy).
const JSONToDate = arr => {
const dt = new Date(parseInt(arr.toString().substr(6)));
return `${dt.getDate()}/${dt.getMonth() + 1}/${dt.getFullYear()}`;
};
Examples
JSONToDate(/Date(1489525200000)/); // "14/3/2017"
speechSynthesis
Performs speech synthesis (experimental).
Use SpeechSynthesisUtterance.voice and window.speechSynthesis.getVoices() to convert a message to speech.
Use window.speechSynthesis.speak() to play the message.
Learn more about the SpeechSynthesisUtterance interface of the Web Speech API.
const speechSynthesis = message => {
const msg = new SpeechSynthesisUtterance(message);
msg.voice = window.speechSynthesis.getVoices()[0];
window.speechSynthesis.speak(msg);
};
Examples
speechSynthesis('Hello, World'); // // plays the message
binarySearch
Use recursion. Similar to Array.indexOf() that finds the index of a value within an array.
The difference being this operation only works with sorted arrays which offers a major performance boost due to it's logarithmic nature when compared to a linear search or Array.indexOf().
Search a sorted array by repeatedly dividing the search interval in half.
Begin with an interval covering the whole array.
If the value of the search is less than the item in the middle of the interval, recurse into the lower half. Otherwise recurse into the upper half.
Repeatedly recurse until the value is found which is the mid or you've recursed to a point that is greater than the length which means the value doesn't exist and return -1.
const binarySearch = (arr, val, start = 0, end = arr.length - 1) => {
if (start > end) return -1;
const mid = Math.floor((start + end) / 2);
if (arr[mid] > val) return binarySearch(arr, val, start, mid - 1);
if (arr[mid] < val) return binarySearch(arr, val, mid + 1, end);
return mid;
}
Examples
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 6); // 2
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 21); // -1
collatz
Applies the Collatz algorithm.
If n is even, return n/2. Otherwise, return 3n+1.
const collatz = n => (n % 2 == 0 ? n / 2 : 3 * n + 1);
Examples
collatz(8); // 4
countVowels
Retuns number of vowels in provided string.
Use a regular expression to count the number of vowels (A, E, I, O, U) in a string.
const countVowels = str => (str.match(/[aeiou]/gi) || []).length;
Examples
countVowels('foobar'); // 3
countVowels('gym'); // 0
factors
Returns the array of factors of the given num.
If the second argument is set to true returns only the prime factors of num.
If num is 1 or 0 returns an empty array.
If num is less than 0 returns all the factors of -int together with their additive inverses.
Use Array.from(), Array.map() and Array.filter() to find all the factors of num.
If given num is negative, use Array.reduce() to add the additive inverses to the array.
Return all results if primes is false, else determine and return only the prime factors using isPrime and Array.filter().
Omit the second argument, primes, to return prime and non-prime factors by default.
Note:- Negative numbers are not considered prime.
const factors = (num, primes = false) => {
const isPrime = num => {
const boundary = Math.floor(Math.sqrt(num));
for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
return num >= 2;
};
const isNeg = num < 0;
num = isNeg ? -num : num;
let array = Array.from({ length: num - 1 })
.map((val, i) => (num % (i + 2) === 0 ? i + 2 : false))
.filter(val => val);
if (isNeg)
array = array.reduce((acc, val) => {
acc.push(val);
acc.push(-val);
return acc;
}, []);
return primes ? array.filter(isPrime) : array;
};
Examples
factors(12); // [2,3,4,6,12]
factors(12, true); // [2,3]
factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12]
factors(-12, true); // [2,3]
fibonacciCountUntilNum
Returns the number of fibonnacci numbers up to num(0 and num inclusive).
Use a mathematical formula to calculate the number of fibonacci numbers until num.
const fibonacciCountUntilNum = num =>
Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
Examples
fibonacciCountUntilNum(10); // 7
30 seconds of code
These snippets , while useful and interesting, didn't quite make it into the repository due to either having very specific use-cases or being outdated. However we felt like they might still be useful to some readers, so here they are.
Table of Contents
- [
JSONToDate.md](#jsontodate.md - [
speechSynthesis.md](#speechsynthesis.md - [
collatz.md](#collatz.md - [
countVowels.md](#countvowels.md - [
factors.md](#factors.md - [
fibonacciCountUntilNum.md](#fibonaccicountuntilnum.md - [
binarySearch.md](#binarysearch.md - [
howManyTimes.md](#howmanytimes.md - [
isArmstrongNumber.md](#isarmstrongnumber.md - [
quickSort.md](#quicksort.md - [
removeVowels.md](#removevowels.md - [
solveRPN.md](#solverpn.md - [
fibonacciUntilNum.md](#fibonacciuntilnum.md
JSONToDate
Converts a JSON object to a date.
Use Date(), to convert dates in JSON format to readable format (dd/mm/yyyy).
const JSONToDate = arr => {
const dt = new Date(parseInt(arr.toString().substr(6)));
return `${dt.getDate()}/${dt.getMonth() + 1}/${dt.getFullYear()}`;
};
Examples
JSONToDate(/Date(1489525200000)/); // "14/3/2017"
speechSynthesis
Performs speech synthesis (experimental).
Use SpeechSynthesisUtterance.voice and window.speechSynthesis.getVoices() to convert a message to speech.
Use window.speechSynthesis.speak() to play the message.
Learn more about the SpeechSynthesisUtterance interface of the Web Speech API.
const speechSynthesis = message => {
const msg = new SpeechSynthesisUtterance(message);
msg.voice = window.speechSynthesis.getVoices()[0];
window.speechSynthesis.speak(msg);
};
Examples
speechSynthesis('Hello, World'); // // plays the message
collatz
Applies the Collatz algorithm.
If n is even, return n/2. Otherwise, return 3n+1.
const collatz = n => (n % 2 == 0 ? n / 2 : 3 * n + 1);
Examples
collatz(8); // 4
countVowels
Retuns number of vowels in provided string.
Use a regular expression to count the number of vowels (A, E, I, O, U) in a string.
const countVowels = str => (str.match(/[aeiou]/gi) || []).length;
Examples
countVowels('foobar'); // 3
countVowels('gym'); // 0
factors
Returns the array of factors of the given num.
If the second argument is set to true returns only the prime factors of num.
If num is 1 or 0 returns an empty array.
If num is less than 0 returns all the factors of -int together with their additive inverses.
Use Array.from(), Array.map() and Array.filter() to find all the factors of num.
If given num is negative, use Array.reduce() to add the additive inverses to the array.
Return all results if primes is false, else determine and return only the prime factors using isPrime and Array.filter().
Omit the second argument, primes, to return prime and non-prime factors by default.
Note:- Negative numbers are not considered prime.
const factors = (num, primes = false) => {
const isPrime = num => {
const boundary = Math.floor(Math.sqrt(num));
for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
return num >= 2;
};
const isNeg = num < 0;
num = isNeg ? -num : num;
let array = Array.from({ length: num - 1 })
.map((val, i) => (num % (i + 2) === 0 ? i + 2 : false))
.filter(val => val);
if (isNeg)
array = array.reduce((acc, val) => {
acc.push(val);
acc.push(-val);
return acc;
}, []);
return primes ? array.filter(isPrime) : array;
};
Examples
factors(12); // [2,3,4,6,12]
factors(12, true); // [2,3]
factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12]
factors(-12, true); // [2,3]
fibonacciCountUntilNum
Returns the number of fibonnacci numbers up to num(0 and num inclusive).
Use a mathematical formula to calculate the number of fibonacci numbers until num.
const fibonacciCountUntilNum = num =>
Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
Examples
fibonacciCountUntilNum(10); // 7
binarySearch
Use recursion. Similar to Array.indexOf() that finds the index of a value within an array.
The difference being this operation only works with sorted arrays which offers a major performance boost due to it's logarithmic nature when compared to a linear search or Array.indexOf().
Search a sorted array by repeatedly dividing the search interval in half.
Begin with an interval covering the whole array.
If the value of the search is less than the item in the middle of the interval, recurse into the lower half. Otherwise recurse into the upper half.
Repeatedly recurse until the value is found which is the mid or you've recursed to a point that is greater than the length which means the value doesn't exist and return -1.
const binarySearch = (arr, val, start = 0, end = arr.length - 1) => {
if (start > end) return -1;
const mid = Math.floor((start + end) / 2);
if (arr[mid] > val) return binarySearch(arr, val, start, mid - 1);
if (arr[mid] < val) return binarySearch(arr, val, mid + 1, end);
return mid;
}
Examples
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 6); // 2
binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 21); // -1
howManyTimes
Returns the number of times num can be divided by divisor (integer or fractional) without getting a fractional answer.
Works for both negative and positive integers.
If divisor is -1 or 1 return Infinity.
If divisor is -0 or 0 return 0.
Otherwise, keep dividing num with divisor and incrementing i, while the result is an integer.
Return the number of times the loop was executed, i.
const howManyTimes = (num, divisor) => {
if (divisor === 1 || divisor === -1) return Infinity;
if (divisor === 0) return 0;
let i = 0;
while (Number.isInteger(num / divisor)) {
i++;
num = num / divisor;
}
return i;
};
Examples
howManyTimes(100, 2); // 2
howManyTimes(100, 2.5); // 2
howManyTimes(100, 0); // 0
howManyTimes(100, -1); // Infinity
isArmstrongNumber
Checks if the given number is an Armstrong number or not.
Convert the given number into an array of digits. Use the exponent operator (**) to get the appropriate power for each digit and sum them up. If the sum is equal to the number itself, return true otherwise false.
const isArmstrongNumber = digits =>
(arr => arr.reduce((a, d) => a + parseInt(d) ** arr.length, 0) == digits)(
(digits + '').split('')
);
Examples
isArmstrongNumber(1634); // true
isArmstrongNumber(56); // false
quickSort
QuickSort an Array (ascending sort by default).
Use recursion.
Use Array.filter and spread operator (...) to create an array that all elements with values less than the pivot come before the pivot, and all elements with values greater than the pivot come after it.
If the parameter desc is truthy, return array sorts in descending order.
const quickSort = ([n, ...nums], desc) =>
isNaN(n)
? []
: [
...quickSort(nums.filter(v => (desc ? v > n : v <= n)), desc),
n,
...quickSort(nums.filter(v => (!desc ? v > n : v <= n)), desc)
];
Examples
quickSort([4, 1, 3, 2]); // [1,2,3,4]
quickSort([4, 1, 3, 2], true); // [4,3,2,1]
removeVowels
Returns all the vowels in a str replaced by repl.
Use String.replace() with a regexp to replace all vowels in str.
Omot repl to use a default value of ''.
const removeVowels = (str, repl = '') => str.replace(/[aeiou]/gi,repl);
Examples
removeVowels("foobAr"); // "fbr"
removeVowels("foobAr","*"); // "f**b*r"
solveRPN
Solves the given mathematical expression in reverse polish notation.
Throws appropriate errors if there are unrecognized symbols or the expression is wrong. The valid operators are :- +,-,*,/,^,** (^&** are the exponential symbols and are same). This snippet does not supports any unary operators.
Use a dictionary, OPERATORS to specify each operator's matching mathematical operation.
Use String.replace() with a regular expression to replace ^ with **, String.split() to tokenize the string and Array.filter() to remove empty tokens.
Use Array.forEach() to parse each symbol, evaluate it as a numeric value or operator and solve the mathematical expression.
Numeric values are converted to floating point numbers and pushed to a stack, while operators are evaluated using the OPERATORS dictionary and pop elements from the stack to apply operations.
const solveRPN = rpn => {
const OPERATORS = {
'*': (a, b) => a * b,
'+': (a, b) => a + b,
'-': (a, b) => a - b,
'/': (a, b) => a / b,
'**': (a, b) => a ** b
};
const [stack, solve] = [
[],
rpn
.replace(/\^/g, '**')
.split(/\s+/g)
.filter(el => !/\s+/.test(el) && el !== '')
];
solve.forEach(symbol => {
if (!isNaN(parseFloat(symbol)) && isFinite(symbol)) {
stack.push(symbol);
} else if (Object.keys(OPERATORS).includes(symbol)) {
const [a, b] = [stack.pop(), stack.pop()];
stack.push(OPERATORS[symbol](parseFloat(b), parseFloat(a)));
} else {
throw `${symbol} is not a recognized symbol`;
}
});
if (stack.length === 1) return stack.pop();
else throw `${rpn} is not a proper RPN. Please check it and try again`;
};
Examples
solveRPN('15 7 1 1 + - / 3 * 2 1 1 + + -'); // 5
solveRPN('2 3 ^'); // 8
fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1).
Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two.
Uses a mathematical formula to calculate the length of the array required.
const fibonacciUntilNum = num => {
let n = Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
return Array.from({ length: n }).reduce(
(acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
[]
);
};
howManyTimes
Returns the number of times num can be divided by divisor (integer or fractional) without getting a fractional answer.
Works for both negative and positive integers.
If divisor is -1 or 1 return Infinity.
If divisor is -0 or 0 return 0.
Otherwise, keep dividing num with divisor and incrementing i, while the result is an integer.
Return the number of times the loop was executed, i.
const howManyTimes = (num, divisor) => {
if (divisor === 1 || divisor === -1) return Infinity;
if (divisor === 0) return 0;
let i = 0;
while (Number.isInteger(num / divisor)) {
i++;
num = num / divisor;
}
return i;
};
Examples
howManyTimes(100, 2); // 2
howManyTimes(100, 2.5); // 2
howManyTimes(100, 0); // 0
howManyTimes(100, -1); // Infinity
isArmstrongNumber
Checks if the given number is an Armstrong number or not.
Convert the given number into an array of digits. Use the exponent operator (**) to get the appropriate power for each digit and sum them up. If the sum is equal to the number itself, return true otherwise false.
const isArmstrongNumber = digits =>
(arr => arr.reduce((a, d) => a + parseInt(d) ** arr.length, 0) == digits)(
(digits + '').split('')
);
Examples
isArmstrongNumber(1634); // true
isArmstrongNumber(56); // false
quickSort
QuickSort an Array (ascending sort by default).
Use recursion.
Use Array.filter and spread operator (...) to create an array that all elements with values less than the pivot come before the pivot, and all elements with values greater than the pivot come after it.
If the parameter desc is truthy, return array sorts in descending order.
const quickSort = ([n, ...nums], desc) =>
isNaN(n)
? []
: [
...quickSort(nums.filter(v => (desc ? v > n : v <= n)), desc),
n,
...quickSort(nums.filter(v => (!desc ? v > n : v <= n)), desc)
];
Examples
quickSort([4, 1, 3, 2]); // [1,2,3,4]
quickSort([4, 1, 3, 2], true); // [4,3,2,1]
removeVowels
Returns all the vowels in a str replaced by repl.
Use String.replace() with a regexp to replace all vowels in str.
Omot repl to use a default value of ''.
const removeVowels = (str, repl = '') => str.replace(/[aeiou]/gi,repl);
Examples
removeVowels("foobAr"); // "fbr"
removeVowels("foobAr","*"); // "f**b*r"
solveRPN
Solves the given mathematical expression in reverse polish notation.
Throws appropriate errors if there are unrecognized symbols or the expression is wrong. The valid operators are :- +,-,*,/,^,** (^&** are the exponential symbols and are same). This snippet does not supports any unary operators.
Use a dictionary, OPERATORS to specify each operator's matching mathematical operation.
Use String.replace() with a regular expression to replace ^ with **, String.split() to tokenize the string and Array.filter() to remove empty tokens.
Use Array.forEach() to parse each symbol, evaluate it as a numeric value or operator and solve the mathematical expression.
Numeric values are converted to floating point numbers and pushed to a stack, while operators are evaluated using the OPERATORS dictionary and pop elements from the stack to apply operations.
const solveRPN = rpn => {
const OPERATORS = {
'*': (a, b) => a * b,
'+': (a, b) => a + b,
'-': (a, b) => a - b,
'/': (a, b) => a / b,
'**': (a, b) => a ** b
};
const [stack, solve] = [
[],
rpn
.replace(/\^/g, '**')
.split(/\s+/g)
.filter(el => !/\s+/.test(el) && el !== '')
];
solve.forEach(symbol => {
if (!isNaN(parseFloat(symbol)) && isFinite(symbol)) {
stack.push(symbol);
} else if (Object.keys(OPERATORS).includes(symbol)) {
const [a, b] = [stack.pop(), stack.pop()];
stack.push(OPERATORS[symbol](parseFloat(b), parseFloat(a)));
} else {
throw `${symbol} is not a recognized symbol`;
}
});
if (stack.length === 1) return stack.pop();
else throw `${rpn} is not a proper RPN. Please check it and try again`;
};
Examples
solveRPN('15 7 1 1 + - / 3 * 2 1 1 + + -'); // 5
solveRPN('2 3 ^'); // 8
fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1).
Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two.
Uses a mathematical formula to calculate the length of the array required.
const fibonacciUntilNum = num => {
let n = Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
return Array.from({ length: n }).reduce(
(acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
[]
);
};
howManyTimes
Returns the number of times num can be divided by divisor (integer or fractional) without getting a fractional answer.
Works for both negative and positive integers.
If divisor is -1 or 1 return Infinity.
If divisor is -0 or 0 return 0.
Otherwise, keep dividing num with divisor and incrementing i, while the result is an integer.
Return the number of times the loop was executed, i.
const howManyTimes = (num, divisor) => {
if (divisor === 1 || divisor === -1) return Infinity;
if (divisor === 0) return 0;
let i = 0;
while (Number.isInteger(num / divisor)) {
i++;
num = num / divisor;
}
return i;
};
Examples
howManyTimes(100, 2); // 2
howManyTimes(100, 2.5); // 2
howManyTimes(100, 0); // 0
howManyTimes(100, -1); // Infinity
isArmstrongNumber
Checks if the given number is an Armstrong number or not.
Convert the given number into an array of digits. Use the exponent operator (**) to get the appropriate power for each digit and sum them up. If the sum is equal to the number itself, return true otherwise false.
const isArmstrongNumber = digits =>
(arr => arr.reduce((a, d) => a + parseInt(d) ** arr.length, 0) == digits)(
(digits + '').split('')
);
Examples
isArmstrongNumber(1634); // true
isArmstrongNumber(56); // false
quickSort
QuickSort an Array (ascending sort by default).
Use recursion.
Use Array.filter and spread operator (...) to create an array that all elements with values less than the pivot come before the pivot, and all elements with values greater than the pivot come after it.
If the parameter desc is truthy, return array sorts in descending order.
const quickSort = ([n, ...nums], desc) =>
isNaN(n)
? []
: [
...quickSort(nums.filter(v => (desc ? v > n : v <= n)), desc),
n,
...quickSort(nums.filter(v => (!desc ? v > n : v <= n)), desc)
];
Examples
quickSort([4, 1, 3, 2]); // [1,2,3,4]
quickSort([4, 1, 3, 2], true); // [4,3,2,1]
removeVowels
Returns all the vowels in a str replaced by repl.
Use String.replace() with a regexp to replace all vowels in str.
Omot repl to use a default value of ''.
const removeVowels = (str, repl = '') => str.replace(/[aeiou]/gi,repl);
Examples
removeVowels("foobAr"); // "fbr"
removeVowels("foobAr","*"); // "f**b*r"
solveRPN
Solves the given mathematical expression in reverse polish notation.
Throws appropriate errors if there are unrecognized symbols or the expression is wrong. The valid operators are :- +,-,*,/,^,** (^&** are the exponential symbols and are same). This snippet does not supports any unary operators.
Use a dictionary, OPERATORS to specify each operator's matching mathematical operation.
Use String.replace() with a regular expression to replace ^ with **, String.split() to tokenize the string and Array.filter() to remove empty tokens.
Use Array.forEach() to parse each symbol, evaluate it as a numeric value or operator and solve the mathematical expression.
Numeric values are converted to floating point numbers and pushed to a stack, while operators are evaluated using the OPERATORS dictionary and pop elements from the stack to apply operations.
const solveRPN = rpn => {
const OPERATORS = {
'*': (a, b) => a * b,
'+': (a, b) => a + b,
'-': (a, b) => a - b,
'/': (a, b) => a / b,
'**': (a, b) => a ** b
};
const [stack, solve] = [
[],
rpn
.replace(/\^/g, '**')
.split(/\s+/g)
.filter(el => !/\s+/.test(el) && el !== '')
];
solve.forEach(symbol => {
if (!isNaN(parseFloat(symbol)) && isFinite(symbol)) {
stack.push(symbol);
} else if (Object.keys(OPERATORS).includes(symbol)) {
const [a, b] = [stack.pop(), stack.pop()];
stack.push(OPERATORS[symbol](parseFloat(b), parseFloat(a)));
} else {
throw `${symbol} is not a recognized symbol`;
}
});
if (stack.length === 1) return stack.pop();
else throw `${rpn} is not a proper RPN. Please check it and try again`;
};
Examples
solveRPN('15 7 1 1 + - / 3 * 2 1 1 + + -'); // 5
solveRPN('2 3 ^'); // 8
fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1).
Use Array.reduce() to add values into the array, using the sum of the last two values, except for the first two.
Uses a mathematical formula to calculate the length of the array required.
const fibonacciUntilNum = num => {
let n = Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
return Array.from({ length: n }).reduce(
(acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
[]
);
};
httpDelete
Makes a DELETE request to the passed URL.
Use XMLHttpRequest web api to make a delete request to the given url.
Handle the onload event, by running the provided callback function.
Handle the onerror event, by running the provided err function.
Omit the third argument, err to log the request to the console's error stream by default.
const httpDelete = (url, callback, err = console.error) => {
const request = new XMLHttpRequest();
request.open("DELETE", url, true);
request.onload = () => callback(request);
request.onerror = () => err(request);
request.send();
};
Examples
httpDelete('https://website.com/users/123', request => {
console.log(request.responseText);
}); // 'Deletes a user from the database'
httpPut
Makes a PUT request to the passed URL.
Use XMLHttpRequest web api to make a put request to the given url.
Set the value of an HTTP request header with setRequestHeader method.
Handle the onload event, by running the provided callback function.
Handle the onerror event, by running the provided err function.
Omit the last argument, err to log the request to the console's error stream by default.
const httpPut = (url, data, callback, err = console.error) => {
const request = new XMLHttpRequest();
request.open("PUT", url, true);
request.setRequestHeader('Content-type','application/json; charset=utf-8');
request.onload = () => callback(request);
request.onerror = () => err(request);
request.send(data);
};
Examples
const password = "fooBaz";
const data = JSON.stringify(password);
httpPut('https://website.com/users/123', data, request => {
console.log(request.responseText);
}); // 'Updates a user's password in database'
isArmstrongNumber
Checks if the given number is an Armstrong number or not.
Convert the given number into an array of digits. Use the exponent operator (**) to get the appropriate power for each digit and sum them up. If the sum is equal to the number itself, return true otherwise false.
const isArmstrongNumber = digits =>
(arr => arr.reduce((a, d) => a + parseInt(d) ** arr.length, 0) == digits)(
(digits + '').split('')
);
Examples
isArmstrongNumber(1634); // true
isArmstrongNumber(56); // false
quickSort
QuickSort an Array (ascending sort by default).
Use recursion.
Use Array.filter and spread operator (...) to create an array that all elements with values less than the pivot come before the pivot, and all elements with values greater than the pivot come after it.
If the parameter desc is truthy, return array sorts in descending order.
const quickSort = ([n, ...nums], desc) =>
isNaN(n)
? []
: [
...quickSort(nums.filter(v => (desc ? v > n : v <= n)), desc),
n,
...quickSort(nums.filter(v => (!desc ? v > n : v <= n)), desc)
];
Examples
quickSort([4, 1, 3, 2]); // [1,2,3,4]
quickSort([4, 1, 3, 2], true); // [4,3,2,1]
removeVowels
Returns all the vowels in a str replaced by repl.
Use String.replace() with a regexp to replace all vowels in str.
Omot repl to use a default value of ''.
const removeVowels = (str, repl = '') => str.replace(/[aeiou]/gi,repl);
Examples
removeVowels("foobAr"); // "fbr"
removeVowels("foobAr","*"); // "f**b*r"
solveRPN
Solves the given mathematical expression in reverse polish notation.
Throws appropriate errors if there are unrecognized symbols or the expression is wrong. The valid operators are :- +,-,*,/,^,** (^&** are the exponential symbols and are same). This snippet does not supports any unary operators.
Use a dictionary, OPERATORS to specify each operator's matching mathematical operation.
Use String.replace() with a regular expression to replace ^ with **, String.split() to tokenize the string and Array.filter() to remove empty tokens.
Use Array.forEach() to parse each symbol, evaluate it as a numeric value or operator and solve the mathematical expression.
Numeric values are converted to floating point numbers and pushed to a stack, while operators are evaluated using the OPERATORS dictionary and pop elements from the stack to apply operations.
const solveRPN = rpn => {
const OPERATORS = {
'*': (a, b) => a * b,
'+': (a, b) => a + b,
'-': (a, b) => a - b,
'/': (a, b) => a / b,
'**': (a, b) => a ** b
};
const [stack, solve] = [
[],
rpn
.replace(/\^/g, '**')
.split(/\s+/g)
.filter(el => !/\s+/.test(el) && el !== '')
];
solve.forEach(symbol => {
if (!isNaN(parseFloat(symbol)) && isFinite(symbol)) {
stack.push(symbol);
} else if (Object.keys(OPERATORS).includes(symbol)) {
const [a, b] = [stack.pop(), stack.pop()];
stack.push(OPERATORS[symbol](parseFloat(b), parseFloat(a)));
} else {
throw `${symbol} is not a recognized symbol`;
}
});
if (stack.length === 1) return stack.pop();
else throw `${rpn} is not a proper RPN. Please check it and try again`;
};
Examples
solveRPN('15 7 1 1 + - / 3 * 2 1 1 + + -'); // 5
solveRPN('2 3 ^'); // 8
howManyTimes
Returns the number of times num can be divided by divisor (integer or fractional) without getting a fractional answer.
Works for both negative and positive integers.
If divisor is -1 or 1 return Infinity.
If divisor is -0 or 0 return 0.
Otherwise, keep dividing num with divisor and incrementing i, while the result is an integer.
Return the number of times the loop was executed, i.
const howManyTimes = (num, divisor) => {
if (divisor === 1 || divisor === -1) return Infinity;
if (divisor === 0) return 0;
let i = 0;
while (Number.isInteger(num / divisor)) {
i++;
num = num / divisor;
}
return i;
};
Examples
howManyTimes(100, 2); // 2
howManyTimes(100, 2.5); // 2
howManyTimes(100, 0); // 0
howManyTimes(100, -1); // Infinity