CODEWITHSUNDEEP
javascriptoop
RylonMcnz
RylonMcnz

Reputation: 53

Why use "this" in OO JavaScript?

I see many people using the "this" keyword in an object oriented context in JavaScript. Similar to how "self" is used in Python and some other languages. In an object oriented context, I have been able to avoid using "this" by using the "module pattern".

For example:

var robot = (function() {
    // private variables
    var status = "on";
    var name;

    // private function
    function turnOff() {
        status = "off";
    }

    // public function
    function setName(new_name) {
        name = new_name;
    }

    return {
        setName: setName
    };
})();

Or, this pattern:

var robot = function(robot_name) {
    // private variables
    var status = "on";
    var name = robot_name;

    // private function
    function turnOff() {
        status = "off";
    }

    // public function
    function setName(new_name) {
        name = new_name;
    }

    return {
        setName: setName
    };
};

var FooBot = new robot('Foo');
var BarBot = new robot('Bar');

Is using "this" just a preference? Or, am I missing out on something?

Upvotes: 0

Views: 81

Answers (1)

Oriol
Oriol

Reputation: 288080

No, this is not a preference. this is useful to know on which object your function was called.

In your example you don't need this information, that's why this is not useful for you.

But consider a constructor with multiple instances, and each one has its own associated data:

class Robot {
  constructor(name) {
    this.status = "on";
    this.setName(name);
  }
  turnOff() {
    this.status = "off";
  }
  setName(new_name) {
    this.name = new_name;
  }
}
var robotFoo = new Robot('foo');
var robotBar = new Robot('bar');

How would you read and store the data of the desired instance without using this?

You could use static methods and pass the instance as an argument, but that would be uglier.

Upvotes: 3

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