how to add string values in javascript code example

Example 1: string concat javascript

//This method adds two or more strings and returns a new single string.

let str1 = new String( "This is string one" ); 
let str2 = new String( "This is string two" ); 
let str3 = str1.concat(str2.toString());
console.log("str1 + str2 : "+str3)

output:
str1 + str2 : This is string oneThis is string two

Example 2: javascript join address to string

var address = "foo";
var city;
var state = "bar";
var zip;

text = [address, city, state, zip].filter(Boolean).join(", ");
console.log(text)