add two string output 9999 return 1818 js code example
Example 1: concat no and string in javascript
['Hello', ' ', 'World'].join(''); // 'Hello World'
Example 2: 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]