return for append string js code example

Example 1: string concatenation in js

var str1 = "Hello ";
var str2 = "world!";
var res = str1.concat(str2);
console.log(res);

Example 2: how to concatenate strings javascript

var str1 = "Hello ";
var str2 = "world!";
var res = str1.concat(str2);
// does not change the existing strings, but
// returns a new string containing the text
// of the joined strings.