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    <p>It's a way of "borrowing" the constructor function of <code>Product</code> to initialize your new <code>Food</code>.</p> <p>When you call a function with <code>new</code>, you're setting <code>this</code> to be the new instance. You're then doing <code>Product.call</code> (i.e. calling the <code>Product</code> function and setting <code>this</code> inside the <code>Product</code> function to be your new <code>Food</code> instance (which is <code>this</code> inside <code>Food</code>)), and passing your <code>name</code> and <code>price</code>.</p> <p>After <code>Product.call(this, name, price);</code> you should find that <code>this.name</code> and <code>this.price</code> have been set.</p> <p>This doesn't allow inheritance, nor do you <em>gain</em> inheritance; it just executes the constructor function <code>Product</code> on your new <code>Food</code> instance. </p> <p>To gain inheritance, you'd also have to set the <code>prototype</code> of <code>Food</code> to be a new <code>Product</code> instance;</p> <pre><code>function Product(name, price) { this.name = name; this.price = price; } Product.prototype.showPriceIn = function (currency) { alert(this.price + currency); } function Food(name, price) { Product.call(this, name, price); this.category = 'food'; } Food.prototype = new Product; var chicken = new Food('chicken','40'); chicken.showPriceIn("$"); </code></pre> <p><a href="http://jsfiddle.net/hPWMN/" rel="nofollow">http://jsfiddle.net/hPWMN/</a></p> <hr> <p><strong>N.B:</strong> Be careful saying that "Bob is invoked with the <strong><em>scope</em></strong> of Alice"; this isn't true. Bob doesn't inherit the scope of Alice, the value of <code>this</code> inside the <code>greet</code> function is merely altered to be <code>Alice</code>. Inheriting the scope would imply Bob gains access to private variables and the like, which he doesn't.</p>
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    1. POJavascript call and apply on constructor functions
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    1. CO+1 Nice post ...
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    2. COI think the main part I don't understand is that when you are calling the Product function inside Food, how does the calling of that function give 'this' of Food the 'name' and 'price' property. Can you explain this part in particular?
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    3. CO@eirikrl: Because the first parameter to `apply()` and `call()` defines what the `this` should be inside the function, right? Inside the `Food` constructor, we're passing `this`, which is the new `Food` instance we've constructed (which you can see as `this.category` is being set to "food"). Therefore, everytime you do `this.something = something` inside `Product` after it has been `call`'d from `Food` the *this* is now the `Food` instance (like it was for `this.category = "food"`).
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