83 lines
2.4 KiB
Markdown
83 lines
2.4 KiB
Markdown
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# 30 seconds of code
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> Curated collection of useful Javascript snippets that you can understand in 30 seconds or less.
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- Use <kbd>Ctrl</kbd> + <kbd>F</kbd> or <kbd>command</kbd> + <kbd>F</kbd> to search for a snippet.
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- Contributions welcome, please read [contribution guide](contributing.md).
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## Contents
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* [Even or odd number](even-or-odd-number.md)
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* [Greatest common divisor gcd](greatest-common-divisor-gcd.md)
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* [RGB to hexadecimal](RGB-to-hexadecimal.md)
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* [Sort characters in string alphabetical](sort-characters-in-string-alphabetical.md)
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* [Sum of array of numbers](sum-of-array-of-numbers.md)
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* [Unique values of array](unique-values-of-array.md)
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### Even or odd number
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Use `Math.abs()` to extend logic to negative numbers, check using the modulo (`%`) operator.
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Return `true` if the number is even, `false` if the number is odd.
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```js
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var isEven = num => Math.abs(num) % 2 === 0;
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```
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## Greatest common divisor (GCD)
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Use recursion.
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Base case is when `y` equals `0`. In this case, return `x`.
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Otherwise, return the GCD of `y` and the remainder of the division `x/y`.
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```js
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var gcd = (x , y) => !y ? x : gcd(y, x % y);
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```
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## RGB to hexadecimal
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Convert each value to a hexadecimal string, using `toString(16)`, then `padStart(2,'0')` to get a 2-digit hexadecimal value.
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Combine values using `join('')`.
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```js
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var rgbToHex = (r, g, b) =>
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[r.toString(16).padStart(2,'0') , g.toString(16).padStart(2,'0') , b.toString(16).padStart(2,'0')].join('');
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```
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### Sort characters in string (alphabetical)
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Split the string using `split('')`, `sort()` utilizing `localeCompare()`, recombine using `join('')`.
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```js
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var sortCharactersInString = str =>
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str.split('').sort( (a,b) => a.localeCompare(b) ).join('');
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```
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### Sum of array of numbers
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Use `reduce()` to add each value to an accumulator, initialized with a value of `0`.
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```js
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var sum = arr =>
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arr.reduce( (acc , val) => acc + val, 0);
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```
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### Unique values of array
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Use `reduce()` to accumulate all unique values in an array.
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Check if each value has already been added, using `indexOf()` on the accumulator array.
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```js
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var uniqueValues = arr =>
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arr.reduce( (acc, val) => {
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if(acc.indexOf(val) === -1)
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acc.push(val);
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return acc;
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}, []);
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```
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## Credits
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*Icons made by [Smashicons](https://www.flaticon.com/authors/smashicons) from [www.flaticon.com](https://www.flaticon.com/) is licensed by [CC 3.0 BY](http://creativecommons.org/licenses/by/3.0/).*
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