My Javascript Object maker

While using my solution to clear, easy to understand and short asynchronous Javascript, I ran into a big problem. I wrote it properly(1), with private variables and all. But, if another part of code called it, the variables would collide. It was just a function. Obvious in retrospect, like most problems!

I need an instance of the function for each call. But, I really don’t like “objects.” I’m not sure why. So, I decided to write an “Object Maker” that will accept a function as an input.

Here it is:

PX.asyncObject = function (spec, my) {
    var that = {};  // declare PRIVATE variables here
    my = my || {};  // Use my.xx for *shared* variables
    if (spec.objName) {
        eval('var ' + spec.objName);    // GLOBAL vars are *more* evil than eval
        window[spec.objName] = spec.newObj;             // Make the function sent into a method named from objName
        that[spec.objName]   = window[spec.objName];    // Make the new method a method of "that"
    } else {
        var go;
        go      = spec.newObj;  // Make the function into a method named "go"
        that.go = go;  // Make "go" a method of "that"
    }
    that.spec = spec;    // Put spec into private vars. call go({vars})
    return that;  // return the new, private, durable object
};

The basic routine and idea came from (surprise) Douglas Crockford’s “Javascript: The Good Parts,” pp. 52-55. It is called a functional constructor.

I use it like this:

PX.asyncObject({
    newObj: function (spec) {
        PX.Rest('GET', sUrl, undefined,
            function (result, o) {
                if (result) {
                    // Code for success
                } else {
                   // Code for failure
                }
                    // Code for both
           }
       );
    }
}).go();

Four lines longer and only a little less readable.

(1) Using a Module (pp. 40-41) from Douglas Crockfords “Javascript: The Good Parts.”