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The “This” Keyword in JavaScript

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The “This” Keyword in JavaScript

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In JavaScript, the “this” keyword is used to refer to an object. In a script, this variable is bound to the object whose property is being set or gotten, or to the object being constructed. When a constructor is invoked, it defaults to returning the object referenced by this. However, it is possible to return another object. If the object referenced by this does not exist, this variable is returned.

JavaScript’s “this” keyword

JavaScript’s “this” keyword can be confusing to programmers, but understanding it will unlock advanced features of the language. This keyword points to the object that a function calls. Its usage is not limited to functions; it can also be used to refer to global objects. It has four rules that define its use.

The ‘this‘ keyword is used to identify the object that will receive an event. Usually, the event handler will bind to the HTML element that will be receiving the event.

JavaScript’s prototype inheritance

JavaScript’s prototype inheritance allows you to pass the same prototype to multiple instances. Instances of the same class inherit properties that are defined on the prototype. When you change the prototype, the changes will be reflected on all instances. Similarly, if you want to make a change to a property on a parent class, you can change it on the prototype.

Inheritance is an important concept in computer programming. Unlike other languages that use a class-based inheritance model, JavaScript uses prototype inheritance instead. This means that each object has a prototype property that points to another object, which inherits its properties and methods. An example is Object.prototype.

JavaScript’s strict mode

JavaScript’s strict mode allows you to specify a mode when writing code. The ‘use strict’ keyword in a script file declares strict mode, which makes the code execute in strict mode for the entire file. In addition, you can also declare strict inside a function, where it has a local scope. This means that only the code within that function will execute in strict mode.

You can also use strict mode to prevent mistyping variables and global objects. In strict mode, assigning to non-existing properties, variables, and objects is not permitted. It also prevents you from using the string ‘eval’ as a variable or the string ‘arguments’ as a variable. Also, you cannot use a with statement to create new objects. In normal JavaScript, global objects are created when you use function calls, but in strict mode, they become undefined.

JavaScript’s default binding

The default binding is a fallback method that enforces binding to the object of a function. It detects the location in the code where the function is called and binds it to that object. If the code contains complex elements, such as two methods separated by a call stack, it is difficult to determine the exact location. When coding a function, make sure you always check whether the closing function has an associated parent object.

This keyword is very important to know. It refers to a reference to an object, whether it’s a constructor, global variable, or function prototype method. It’s also used to specify the order in which a function is called. This is a confusing topic for new developers, but it’s an important one.