WARNING - dangerous use of the global this object?

Question

Google closure compiler complains about this code:

function Message() {
    this.message = "";
    this.nickname = "";
    this.time = 0;
    this.my = false;
};

What is dangerous here? How else it is supposed to create "objects"? For now I do

var m = new Message();

to get an initialized object of "type" Message.

score 3 · Accepted Answer · answered Apr 27 '16 at 11:52

3

Try annotating the code to tell the compiler that this is a constructor function:

/**
 * A message
 * @constructor
 */
function Message() {
    this.message = "";
    this.nickname = "";
    this.time = 0;
    this.my = false;
};

answered Apr 27 '16 at 11:52

Ozrix

Yes, this is an option, but I am interested in roots of the problem. What crime the google closure compiler has detected there? – pavelkolodin Apr 27 '16 at 11:56
1

the compiler thinks you are referring to the window object, not the instance of Message, because it doesn't know if Message is a constructor or not – Ozrix Apr 27 '16 at 11:57
one of the basic features of compilers is type checking, that's why you need to annotate. – Ozrix Apr 27 '16 at 12:03
1

@pavelkolodin in ES5, there is no way to determine whether a function is a constructor or not until it's used so you have to add a constructor annotation. ES6 classes take care of this. The error comes from `var m = Message() //no new` – Chad Killingsworth Apr 27 '16 at 22:29

1 Answers1