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'this' keyword in JavaScript

debajit13 profile image Debajit Mallick ・2 min read

If you are new to the world of JavaScript, then you may find 'this' keyword a little bit tricky. In this blog, I will discuss some basics of 'this' keyword, how we can use and its problems.

What is 'this'?

Generally, this keyword refers to the object it belongs to or the parent object. Now, it also varies on which context we use it. Like, in a method, 'this' refers to its parent object. Alone, 'this' refers to the global object. In a function, 'this' refers to the global object. But in a function with 'strict' mode, 'this' refers to undefined. In an event, 'this' refers to the element that received the event. Ex:-

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But sometimes it creates a lot of confusion. Ex:-

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When we are using 'this' in the setTimeout it creates its context for 'this'. So it isn't able to access 'this' of the outer scope and bound to its scope. As 'this' is not defined within the function, the output is undefined. There are two ways to resolve this problem.

  • Using another variable: We can create another variable inside the function and use that to access id.

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  • Using the arrow function: We can also use the arrow function to resolve this problem. As the arrow function doesn't create its own context of 'this', we can access the 'this' of its parent.

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Discussion (6)

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Valeria

One can also use bind method to attach different this to a function or use call or apply to execute function with specified this.

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Debajit Mallick Author

That's great! thank you, Valeria, I will surely try these methods also.

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bruce_taotao • Edited

Wow,that's greate, Thank you

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Iryna Zaletko

In the first example, there is an error in the fname and firstName

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Debajit Mallick Author

Thank you, Iryna for mentioning that error.