opposite of split javascript code example

Example 1: javascript explode space

var str   = "my car is red";
var stringArray = str.split(/(\s+)/);

console.log(stringArray); // ["my", " ", "car", " ", "is", " ", "red"]

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)