PHP's http_build_query equivalent with RFC3986 for JavaScript ES5

http_build_query.js

function http_build_query(data, numeric_prefix, arg_separator, encoding_type_RFC1738) {
    var i = 0, j = 0, encoded_key, encoded_val, query = [];
    if (typeof arg_separator === "undefined") {
        arg_separator = "&";
    }
    for (var key in data) {
        if (data.hasOwnProperty(key)) {
            var value = data[key];
            if (Object.prototype.toString.call(value) === "[object Array]") {
                for (var i = 0; i < value.length; i++) {
                    encoded_key = encodeURIComponent(key + "[]");
                    encoded_val = encodeURIComponent(value[i].toString());
                    if (numeric_prefix && !isNaN(key)) {
                        encoded_key = numeric_prefix + j;
                        j++;
                    }
                    query.push(encoded_key + "=" + encoded_val);
                }
            } else {
                encoded_key = encodeURIComponent(key);
                encoded_val = encodeURIComponent(value.toString());
                if (numeric_prefix && !isNaN(key)) {
                    encoded_key = numeric_prefix + j;
                    j++;
                }
                query.push(encoded_key + "=" + encoded_val);
            }
        }
    }
    query = query.join(arg_separator);
    if (encoding_type_RFC1738) {
        query = decodeURIComponent(query);
    }
    return query;
}

Default is RFC_3986 (%20 for space), unlike PHP's default of RFC_1738 (+ for space).

http_build_query({a: 'ace', b: 'boss of ace'});

a=ace&b=boss%20of%20ace

http_build_query({a: 'ace', b: 'boss of ace'}, '', '&', true);

a=ace&b=boss+of+ace

http_build_query({a: 'ace', b: 'boss of ace', 0: 'boom'}, '', '&', 1);

0=boom&a=ace&b=boss+of+ace

http_build_query({a: 'ace', b: 'boss of ace', 0: 'boom'}, 'var_');

var_0=boom&a=ace&b=boss%20of%20ace

http_build_query({a: 'ace', b: 'boss of ace', ids: [12,34,56], 0: 'boom', 1: 'pow'}, 'var_', '&', 1);

var_0=boom&var_1=pow&a=ace&b=boss+of+ace&ids%5B%5D=12&ids%5B%5D=34&ids%5B%5D=56

http_build_query({a: 'ace', b: 'boss of ace', ids: [12,34,56], 0: 'boom', 1: 'pow'}, 'var_');

var_0=boom&var_1=pow&a=ace&b=boss%20of%20ace&ids%5B%5D=12&ids%5B%5D=34&ids%5B%5D=56

http_build_query({a: 'ace', b: 'boss of ace', ids: [12,34,56], 0: 'boom', 1: 'pow'});

0=boom&1=pow&a=ace&b=boss%20of%20ace&ids%5B%5D=12&ids%5B%5D=34&ids%5B%5D=56

decodeURIComponent(http_build_query({a: 'ace', b: 'boss of ace', ids: [12,34,56], 0: 'boom', 1: 'pow'}));

0=boom&1=pow&a=ace&b=boss of ace&ids[]=12&ids[]=34&ids[]=56

decodeURIComponent(http_build_query({a: 'ace', b: 'boss of ace', ids: [12,34,56], 0: 'boom', 1: 'pow'}, '', '&', 1));

0=boom&1=pow&a=ace&b=boss+of+ace&ids[]=12&ids[]=34&ids[]=56