how to append a string 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: append string js

var s = "1"
s += "2"

Example 3: string concat in js

let string1 = "Hello"
let string2 = "World"

let finalString = string1 + ", " + string2 + "!" // Hello, World!