string concatenation in js using $ 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 concatenation

// the fastest way to string concat in cycle when number of string is less than 1e6
// see https://medium.com/@devchache/the-performance-of-javascript-string-concat-e52466ca2b3a
// see https://www.javaer101.com/en/article/2631962.html
function concat(arr) {
    let str = '';
    for (let i = 0; i < arr.length; i++) {
        str += arr[i];
    }

    return str;
}