CODEWITHSUNDEEP
javascriptthis
GauravP
GauravP

Reputation: 61

Is "this" really a keyword in Javascript?

I have a working piece of code until I added a last property to it. I know the issues of this in javascript. But this is something I have never encounter before.

var name = "John Dane";
var age = 24;

var person = {
  id: 'emp133y1998',
  name, age,
  forEach: function(action) {
    for (var prop in this) {
      if(prop === 'forEach') continue;
      action(this[prop]);
    }
  },
  this: name +" "+ age
};

person.forEach(e => say(e));

If this is keyword how can we use it as a property name. Even stranger thing is I can actually access it person.this like this. But unfortunately my forEach method broke after this. So I removed it. I'm still in learning phase. Can anyone explain what is actually happening here?

Upvotes: 1

Views: 89

Answers (1)

GibboK
GibboK

Reputation: 73928

this is a reserved keywords as of ECMAScript 2015 specification.

The language allow you to declare a property name with a reserved keywords using bracket syntax or not as mention by @squint.

Notes: Naked use of reserved words is supported from ES5 onwards not before.

Example valid for browser enviroment:

// this code works on before ES5 and onward
// this bracket syntax for maximum portability of your code
var obj = {};
obj['this'] = 'hello i am this'; // bracket syntax
obj['for'] = 'hello i am for';
alert(obj['this']);
alert(obj['for']);

// this code works on ES5 and onward
var obj = {};
obj.this = 'hello i am this'; // bracket syntax
obj.for = 'hello i am for';
alert(obj.this);
alert(obj.for);

IMO: I suggest to DO NOT use this or other reserved keywords as a name of a property as could create subtitle bugs and could be confusing to human and build tools.

Upvotes: 2

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