Function Call

JavaScript Function Call

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Functions are Object Methods

All JavaScript functions are object methods.
If a function is not a method of a JavaScript object, it is a function of the global object (see previous chapter).
The example below creates an object with 3 properties (firstName, lastName, fullName).

Example

var person = {
    firstName:"John",
    lastName: "Doe",
    fullName: function () {
        return this.firstName + " " + this.lastName;
    }
}
person.fullName();         // Will return "John Doe"

The fullName property is a method. The person object is the owner of the method.
The fullName property is a method of the person object.

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The JavaScript call() Method

The call() method is a predefined JavaScript function method.
It can be used to invoke (call) a function with an owner object as the first argument (parameter).

With call(), you can use a method belonging to another object.

This example calls the fullName function of person, but is using it on myObject:

Example

var person = {
    firstName:"John",
    lastName: "Doe",
    fullName: function() {
        return this.firstName + " " + this.lastName;
    }
}
var myObject = {
    firstName:"Mary",
    lastName: "Doe",
}
person.fullName.call(myObject);  // Will return "Mary Doe" 

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