use concat in javascript code example

Example 1: string concatenation in js

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

Example 2: javascript join 2 variables into string

A = 'hello ';
B = 'world!';

// outputs "hello world!"
console.log(A + B);