JavaScript: How to join / combine two arrays to concatenate into one array?

Solution 1:

var a = ['a','b','c'];
var b = ['d','e','f'];
var c = a.concat(b); //c is now an an array with: ['a','b','c','d','e','f']
console.log( c[3] ); //c[3] will be 'd'

Solution 2:

Using modern JavaScript syntax - spread operator:

const a = ['a', 'b', 'c'];
const b = ['d', 'e', 'f'];

const c = [...a, ...b]; // c = ['a', 'b', 'c', 'd', 'e', 'f']

It is also the fastest way to concatenate arrays in JavaScript today.