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Arrays

JS oneliners

demo.js Raw #

// Clone array
const _arr = [0, 1, 2];
const arr = [..._arr];
// arr => [0, 1, 2]


// Merge array
const arr1 = [0, 1, 2];
const arr2 = [3, 4, 5];
const arr = [...arr1, ...arr2];
// arr => [0, 1, 2, 3, 4, 5];


// Deduplicated array
const arr = [...new Set([0, 1, 1, null, null])];
// arr => [0, 1, null]


// Obfuscated / randomize array
const arr = [0, 1, 2, 3, 4, 5].slice().sort(() => Math.random() - .5);
// arr => [3, 4, 0, 5, 1, 2]


// Empty array
const arr = [0, 1, 2];
arr.length = 0;
// arr => []


// Insert member at the beginning of the array
let arr = [1, 2];
arr.unshift(0);
arr = [0].concat(arr);
arr = [0, ...arr];
// arr => [0, 1, 2]


// Insert members at the end of the array
let arr = [0, 1]; 
arr.push(2);
arr.concat(2);
arr[arr.length] = 2;
arr = [...arr, 2];
// arr => [0, 1, 2]


// Count number of array members
const arr = [0, 1, 1, 2, 2, 2];
const count = arr.reduce((t, v) => {
 t[v] = t[v] ? ++t[v] : 1;
 return t;
}, {});
// count => { 0: 1, 1: 2, 2: 3 }


// Get random array member
const arr = [0, 1, 2, 3, 4, 5];
const randomItem = arr[Math.floor(Math.random() * arr.length)];
// randomItem => 1


// Create an array of specified length
const arr = [...new Array(3).keys()];
// arr => [0, 1, 2]

const arr = new Array(3).fill(0);
// arr => [0, 0, 0]