customjson.js

function customJSONStringify(value) {

    function writeJSON(value) {

        switch (toType(value)) {
            case "object":
                return writeObject(value);

            case "array":
                return writeArray(value);

            //...
        }

    }

    function writeObject(value) {
        result = '{';
        for (var k in value.keys()) {
            result += '"' +  k + '": ' + writeJson(value[k]) + ', '
        }
        result += "}";
        return result;
    }

    function writeArray(value) {
        result = '[';

        result += ']';
        return result;
    }

    function writeString(value) {

    }

    function writeNumber(value) {

    }

    function writeBoolean(value) {

    }

    function writeNull(value) {

    }

    // https://javascriptweblog.wordpress.com/2011/08/08/fixing-the-javascript-typeof-operator/
    function toType(obj) {
        return ({}).toString.call(obj).match(/\s([a-zA-Z]+)/)[1].toLowerCase();
    }

    return writeJSON(value);
}