Calling a function in javascript file

If a function is not a method of a JavaScript object, it is a function of the global object see previous chapter. In a function definition, this refers to the "owner" of the function. In the example above, this is the person object that "owns" the fullName function. In other words, this. Read more about the this keyword at JS this Keyword. That being the case, this is a more specialized case of how to call a function.

We are calling this function with the intent of creating something new and getting it back. In this example, we have added an input text box so that the user can enter their name. Once again, when our button is clicked we call the sayHello function.

In our sayHello function, we grab the value in the text box and create a new instance of the Greeter object by calling new Greeter. The new keyword and the capital G make it clear that this function is being called as a constructor. When a function is called in this way, this is set to the newly created object. We then add a name property to the newly created object and set its value to the parameter that was passed to the constructor.

The newly created object is passed back to the calling code and saved in the grtr variable. Finally, in the call to console. One thing to always keep in mind when working with functions in JavaScript is that they are first-class objects.

That means that a function can have its own properties and its own methods. Yes, you read that correctly. A function can have its own methods. The call and apply methods are two of those methods. The call and apply methods allow you to specify the context in which the function will execute. They allow you to set the this value. In this code, we start by defining a couple of variables.

An empty array that we will populate with a couple of Person objects and a name. We set its type to text and value with a circle area. The appendChild function appends a new node that behaves like the last child of a node. The document. This example code is exporting calcArea function from first.

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