How can I pass an object into a function's prototype in Javascript?

Question

How can I pass an object into a function's prototype in Javascript?

In my quest to delve deeper into JavaScript, I've embarked on creating my very own MVC library. My current investigation involves examining the source code of backbone.js which can be found here.

When defining a Collection in backbone.js, it involves assigning it to a JavaScript variable as shown below:

var AppCollection = Backbone.Collection.extend({ model: BACKBONE_MODEL })

The creator employs underscore internally and utilizes the `prototype` for the `Collection`, extending it with underscore's `_.extend()` method like so:

_.extend(Collection.prototype, Events, {})

. The empty object passed in serves as a container for all the methods related to the Collection object, such as the `model` key containing the Model object previously defined.

I'm intrigued by the idea of sidestepping the underscore dependency and incorporating my custom prototypical methods for the Collection. How can I introduce an object with the `model` key into my Collection object?

Below is a snippet of what I've been working on:

(function(Pigeon, root, factory) {
    root[Pigeon] = factory();
} ('Pigeon', this, function() {

    var Pigeon = {};

    // Model
    var Model = Pigeon.Model = function() {
        this.attributes = {};
    };

    // Collection
    var Collection = Pigeon.Collection = function(models) {

    };

    // View
    Pigeon.View = {};

    // Controller
    Pigeon.Controller = {};

    return Pigeon;

}));

javascript backbone.js

Answer 1

Answer №1

Instead of relying on "_", there are alternative methods available for extending an object or class without using "_.extend()".

One option is to utilize Object.assign for extending prototypes, although this approach may not be fully supported by all browsers (especially Internet Explorer). Another alternative is to create a custom extend function using Object.keys(mixinClass).

Example using Object.assign:

function a() {
  this.propOne = "one";
}

a.prototype.methodOne = function() {
  document.write("<br/>I am methodOne from a");
}

function b() {
  this.propTwo = "two";
}

b.prototype.methodTwo = function() {
  document.write("<br/>I am methodTwo from b");
}

function assigned() {
  a.call(this);
  b.call(this);
}

// Combine properties from different objects and set constructor
Object.assign(assigned.prototype, a.prototype, b.prototype);
assigned.constructor = assigned;

var x = new assigned();
document.write("<pre>I am assigned and I look like: \n" + JSON.stringify(x, 2, null) + "</pre>");
x.methodOne();
x.methodTwo();

Custom extend function example:

function myExtend() {
  var args = Array.prototype.slice.apply(arguments);
  var target = args.shift();
  var extended = {};
  args.forEach(function(o) {
    Object.keys(o).forEach(function(k) {
      extended[k] = o[k];
    });
  });
  Object.keys(extended).forEach(function(k) {
    if (!target[k])
      target[k] = extended[k];
  });
}

function a() {
  this.propOne = "one";
}

a.prototype.methodOne = function() {
  document.write("<br/>I am methodOne from a");
}

function b() {
  this.propTwo = "two";
}

b.prototype.methodTwo = function() {
  document.write("<br/>I am methodTwo from b");
}

function assigned() {
  a.call(this);
  b.call(this);
}

myExtend(assigned.prototype, a.prototype, b.prototype);
assigned.constructor = assigned;

var x = new assigned();
document.write("<pre>I used myExtend and I look like: \n" + JSON.stringify(x, 2, null) + "</pre>");
x.methodOne();
x.methodTwo();

This technique involves mixin where you can extend simple objects or combine multiple classes to create a subclass with methods of various types. However, keep in mind that this approach creates copies of the properties and methods instead of using references. Nevertheless, it should serve your purpose effectively.

Answer 2

Instead of relying on "_", there are alternative methods available for extending an object or class without using "_.extend()".

One option is to utilize Object.assign for extending prototypes, although this approach may not be fully supported by all browsers (especially Internet Explorer). Another alternative is to create a custom extend function using Object.keys(mixinClass).

Example using Object.assign:

function a() {
  this.propOne = "one";
}

a.prototype.methodOne = function() {
  document.write("<br/>I am methodOne from a");
}

function b() {
  this.propTwo = "two";
}

b.prototype.methodTwo = function() {
  document.write("<br/>I am methodTwo from b");
}

function assigned() {
  a.call(this);
  b.call(this);
}

// Combine properties from different objects and set constructor
Object.assign(assigned.prototype, a.prototype, b.prototype);
assigned.constructor = assigned;

var x = new assigned();
document.write("<pre>I am assigned and I look like: \n" + JSON.stringify(x, 2, null) + "</pre>");
x.methodOne();
x.methodTwo();

Custom extend function example:

function myExtend() {
  var args = Array.prototype.slice.apply(arguments);
  var target = args.shift();
  var extended = {};
  args.forEach(function(o) {
    Object.keys(o).forEach(function(k) {
      extended[k] = o[k];
    });
  });
  Object.keys(extended).forEach(function(k) {
    if (!target[k])
      target[k] = extended[k];
  });
}

function a() {
  this.propOne = "one";
}

a.prototype.methodOne = function() {
  document.write("<br/>I am methodOne from a");
}

function b() {
  this.propTwo = "two";
}

b.prototype.methodTwo = function() {
  document.write("<br/>I am methodTwo from b");
}

function assigned() {
  a.call(this);
  b.call(this);
}

myExtend(assigned.prototype, a.prototype, b.prototype);
assigned.constructor = assigned;

var x = new assigned();
document.write("<pre>I used myExtend and I look like: \n" + JSON.stringify(x, 2, null) + "</pre>");
x.methodOne();
x.methodTwo();

This technique involves mixin where you can extend simple objects or combine multiple classes to create a subclass with methods of various types. However, keep in mind that this approach creates copies of the properties and methods instead of using references. Nevertheless, it should serve your purpose effectively.

How can I pass an object into a function's prototype in Javascript?

Answer №1

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