Encode data into a query string for a GET or POST request, in JavaScript ES5

encodeQueryString.js

function encodeQueryString(params, isPostRequest) {
    var query = new Array();
    for (var key in params) {
        if (params.hasOwnProperty(key)) {
            var value = params[key];
            if (Object.prototype.toString.call(value) === "[object Array]") {
                for (var i = 0, n = value.length; i < n; i++) {
                    query.push(encodeURIComponent(key + "[]") + "=" + encodeURIComponent(value[i]));
                }
            } else {
                query.push(encodeURIComponent(key) + "=" + encodeURIComponent(value));
            }
        }
    }
    query = query.join("&");
    if (isPostRequest) {
        query = query.replaceAll("%20", "+");
        query = decodeURIComponent(query);
    }
    return query;
}

Useful for sending data in a regular GET request, an AJAX GET request, or an AJAX POST request.

var data = {name: "Dr. Jim Lee, MD", ids: [1,2,3], integer: 9, isActive: true}

encodeQueryString(data); // For a GET request

'name=Dr.%20Jim%20Lee%2C%20MD&ids%5B%5D=1&ids%5B%5D=2&ids%5B%5D=3&integer=9&isActive=true'

encodeQueryString(data, true); // For a POST request

'name=Dr.+Jim+Lee,+MD&ids[]=1&ids[]=2&ids[]=3&integer=9&isActive=true'