Converts a JavaScript value to a JSON string

stringify.js

  // This is a reference to JSON.stringify and provides a polyfill for old browsers.
  // stringify serializes an object, array or primitive value and return it as JSON.
  var stringify = (function() {
    var _PRIMITIVE, _OPEN, _CLOSE;
    if (window.JSON && typeof JSON.stringify === "function")
      return JSON.stringify;

    _PRIMITIVE = /string|number|boolean|null/;

    _OPEN = {
      object: "{",
      array: "["
    };

    _CLOSE = {
      object: "}",
      array: "]"
    };

    //gets the type
    function getType(value) {
      if (value === null) return "null";
      if (value instanceof Array) return "array";
      return typeof value;
    }

    //actions to execute in each iteration
    function action(key, value) {
      var type = getType(value),
        prop = "";

      //key is not an array index
      if (typeof key !== "number")
        prop = '"' + key + '":';
      if (type === "string") {
        prop += '"' + value + '"';
      } else if (_PRIMITIVE.test(type)) {
        prop += value;
      } else if (type === "array" || type === "object") {
        prop += toJson(value, type);
      } else return;
      this.push(prop);
    }

    //iterates over an object or array
    function each(obj, callback, thisArg) {
      for (var key in obj) {
        if (obj instanceof Array) key = +key;
        callback.call(thisArg, key, obj[key]);
      }
    }

    //generates the json
    function toJson(obj, type) {
      var items = [];
      each(obj, action, items);
      return _OPEN[type] + items.join(",") + _CLOSE[type];
    }

    //exported function that generates the json
    return function stringify(obj) {
      if (!arguments.length) return "";
      var type = getType(obj);
      if (_PRIMITIVE.test(type))
        return (obj === null ? type : obj.toString());
      //obj is array or object
      return toJson(obj, type);
    }
  }());

test.js

var myObject = {
    "0": null,
    "total-items": 10,
    "undefined-prop": void(0),
    sorted: true,
    images: ["bg-menu.png", "bg-body.jpg", [1, 2]],
    position: { //nested object literal
        "x": 40,
        "y": 300,
        offset: [{ top: 23 }]
    },
    onChange: function() { return !0 },
    pattern: /^bg-.+\.(?:png|jpe?g)$/i
};

var json = stringify(myObject);