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JavaScript Object-Oriented JavaScript (2015) Constructor Functions and Prototypes Creating Multiple Instances with Constructors

Posted by alborz
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alborz
Full Stack JavaScript Techdegree Graduate 30,885 Points

Does "this" always create an instance of an object?

Is "this", when used inside of a function, always creating an instance of an object? Is that what makes it a constructor function?

1 Answer

Brendan Whiting
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Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Points

this doesn't create an object. It's a reference to an object that already exists, the object whose method you're calling. In the context of a constructor function, this refers to the instance that you're in the middle of making.

alborz
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alborz
Full Stack JavaScript Techdegree Graduate 30,885 Points

The object whose method you're calling, or just setting a property, right?

Brendan Whiting
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Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Points

I've been pretty deep lately in the ES6 syntax where there is an explicit constructor method: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes

I'll leave it to someone else to explain how it's actually working under the hood in ES5. But at any rate, it's the new keyword that makes a new instance, this refers to that instance.

Brendan Whiting
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Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Points

PS Treehouse has a workshop on 'this': https://teamtreehouse.com/library/understanding-this-in-javascript