JavaScript Object Methods

By | October 1, 2021

As objects in JavaScript are used to represent real-world objects, the object methods are the functions that a real-world object can perform.

Let’s say a man is an object and he has many properties and some functions that he can perform. All those functions that an object can perform can be implemented using methods.

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The method is a fancy technical term used to define functions in the object.

Like the object properties, we learned in the previous tutorial where we assign name:value pairs in the Object. Where name is a variable name and value is a data value. But in the case of methods, we define value as a function expression.

Syntax

declaration object_name = {method_name: function() {//function body} }

Example

<script>
    var man = {
        name: "Rahul",
        age: 20,

        //method
        is_adult: function()
            { 
                return this.age>=18?true:false;
            }
    }
</script>

Behind the code

In the above example is_adult is the method of man object. In the example, you can see that is_adult property name defines a function that returns true if the this.age value is greater than or equal to 18 else it returns false.

In the example, we have used the if..else ternary operator which is a shorthand to write the if-else statement.

Inside the function/method body you can also notice that there I have used this.age statement to access the age property of the object man instead of directly using age. We will be covering this keyword further in this tutorial. Before that let’s see how can we access an object method.

Access JS Object Methods

Methods are nothing, just the properties of an object which are defined as functions. And similar to the normal function calling we use the method name and parenthesis to call a method.

But there is a slight difference, to call a method we use the dot operator between the object name and method calling. So the JS interpreter could understand we are calling the method that is defined inside a specific object.

Syntax

object_name.method_name()

Example

<script>
    var man = {
        name: "Rahul",
        age: 20,

        //method
        is_adult: function()
            { 
                return this.age>=18?true:false;
            }
    }

    console.log(man.is_adult()); // true
</script>

JavaScript this keyword

this is the most important keyword of JavaScript, in JavaScript, everything is an object, which means complete JavaScript revolves around the concept of objects. The objects we are learning right now are the building structure of all JavaScript concepts.

And the this keyword is used when we are trying to access a property of the object inside the object method.

this keyword tells the function to use the already defined name:value property of the object. Behind the scene this represent the object itself, in the above example, we have used this.age to access the age property of the man object inside the is_aldult method body. There this represents man so this.age inside the method was equivalent to man.age .

So instead of this.age we could have used man.age inside the is_adult method body.

Without using this keyword or object name itself we can not access the property object property inside the method.

Summary

  • methods are the functions defined inside the object.
  • to access a method we can use the object name, dot operator followed by the method name, and parenthesis.
  • this keyword helps the method to access the property of the object.

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