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