How to build query string with Javascript

Question

Just wondering if there is anything built-in to Javascript that can take a Form and return the query parameters, eg: "var1=value&var2=value2&arr[]=foo&arr[]=bar..."

I've been wondering this for years.

Answer 1

2k20 update: use Josh's solution with URLSearchParams.toString().

Old answer:

---

Without jQuery

var params = {
    parameter1: 'value_1',
    parameter2: 'value 2',
    parameter3: 'value&3' 
};

var esc = encodeURIComponent;
var query = Object.keys(params)
    .map(k => esc(k) + '=' + esc(params[k]))
    .join('&');

For browsers that don't support arrow function syntax which requires ES5, change the .map... line to

    .map(function(k) {return esc(k) + '=' + esc(params[k]);})