appending to string javascript code example

Example 1: how the concat function works javascript

var arr = [1, 2, 3, 4];
var arr2 = [5, 6, 7, 8];

const both = arr.concat(arr2);

console.log(both);
//[1, 2, 3, 4, 5, 6, 7, 8]

Example 2: javascript add to string

var s = 'hell'
s = s + 'o'