How is the 'this' keyword of javascript is different from 'this' keyword of java?any practical example will be appreciated.

var counter = {
  val: 0,
  increment: function () {
    this.val += 1;
  }
};
counter.increment();
console.log(counter.val); // 1
counter['increment']();
console.log(counter.val); // 2

in java:

 public Rectangle(int x, int y, int width, int height) {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    }

thanks.

How is the 'this' keyword of javascript is different from 'this' keyword of java?any practical example will be appreciated.

var counter = {
  val: 0,
  increment: function () {
    this.val += 1;
  }
};
counter.increment();
console.log(counter.val); // 1
counter['increment']();
console.log(counter.val); // 2

in java:

 public Rectangle(int x, int y, int width, int height) {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    }

thanks.

• java
• javascript

• 2 this key word in both case refer the current object. – Subhrajyoti Majumder Commented Dec 23, 2013 at 4:56
• 1 In javascript, this can also refer to an element triggering an event. – user1890615 Commented Dec 23, 2013 at 4:59
• 8 Java is not Javascript, so I think comparison you are doing is, between apples and oranges, which doesn't make sense. – kosa Commented Dec 23, 2013 at 4:59
• possible duplicate of java programming language. (I know that is a "closed" Question, but the first Answer clearly and succinctly answers this one too.) – Stephen C Commented Dec 23, 2013 at 5:01
• In ECMAScript, this is set either by the call or using bind. It can reference any object and be different for each call. In addition, in strict mode, this can be set to any value by the call, including undefined. – RobG Commented Dec 23, 2013 at 5:02

3 Answers 3

In JavaScript this always refers to the “owner” of the function we're executing, or rather, to the object that a function is a method of.

In Java, this refers to the current instance object on which the method is executed.

JavaScript is a bit peculiar when it comes to the keyword "this".

In JavaScript, functions are objects, and the value of "this" depends on how a function is called.

In fact, just read the linked article to understand how JavaScript treats the "this" keyword--drink plenty of coffee first.

ECMAScript defines this as a keyword that "evaluates to the value of the ThisBinding of the current execution context" (§11.1.1). The interpreter updates the ThisBinding whenever establishing an execution context.

In Java this refers to the current instance of the method on which it is used. There is a JVM, and no interpreter.