string concatenation in javascript with variables code example

Example 1: js string concatenation es6

let str=`JavaScript first appeared ${a+b} years ago. Wow!`;

Example 2: string concatenation in js

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

Example 3: string javascript concatenation

var dest = new String("");
    var src = new String("aze");
    var ar = new Array();
    ...
    ar.push(src);
    ar.push(src);
    ...
    dest = ar.join("");