How do you call parent object functions from child objects in javascript

extend, javascript, jquery, prototype

Solution

You can use `call` or `apply` i.e.

template_manager.prototype = {
    set: function (tags, template_name) {
        template_name = "Greetings!";
        template_name = this._util.optional.call(this, this.nothing, this.default_template);
        console.log(template_name);
    }
}

See "Getting Out of Binding Situations in JavaScript" article for more explicit explanation.

Problem

So, I was reading up on John Resig's blog, saw his micro-templating javascript engine and decided to try and implement my own template management system for javascript, to deepen my understanding of prototype inheritance. However, the minute I started writing it, I ran into a problem. To start off, here is my base code: ``` function template_manager() { }; template_manager.prototype = { tags: {}, templates: {}, output: {}, default_template: "default", set: function (tags, template_name) { template_name = "Greetings!"; //template_name = this._util.template(this.nothing, this.default_template); console.log(template_name); }, get: function(tags, template_name) { console.log("Getting"); }, unset: function(tags, template_name) { console.log("Removing"); }, render: function(template_name) { console.log("Rendering"); }, //_util goes here }; // Take it for a quick test drive. test = new template_manager; test.set(); test.get(); test.unset(); test.render(); ``` Then I started working on some common code, and I decided to put it into a utility object: ``` _util: { // Used to set the default values for optional arguments optional: function(obj, def_value) { return (typeof obj === "nothing") ? obj : def_value; }, template: function(template_name) { return this._util.optional(template_name, this.default_template); }, }, ``` And now, when I try to call my `_util.template()` function in my `set()` function I of course get an error because `this` points to the `_util` object rather than the `template_manager` object. I've take a look at the jQuery `extend` method, and I think that I understand what it's doing. My question is, do I need to implement my own / use jQuery's `extend` method, or is there another way for me to call the `template_manager` object from my `_util` object? (P. S. I've looked at Douglas Crockford's article on prototype inheritance, and I think the answer is there, but I'm afraid I don't fully understand it yet.)

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