I know there are a lot of "how do I avoid this warning" questions, but it looks like mine is the first specific to JavaScript. In this case, I want to reference the thing I'm initializing inside its own declaration, like so:

var foo = new Foo({
  bar: new Bar({
    x: function(){
      doStuff(foo);
    }
  });
});

(If this looks familiar, maybe you've used ExtJS before -- this is how most of their stuff is built.)

When I call foo.bar.x(), I want to point back to the Foo (foo) that owns the Bar (bar) that's calling the function (x). This works, but my Eclipse warns me that "foo may not have been initialized", referencing the call to doStuff(); -- because, when the engine first sees the line, we haven't finished defining foo yet. Of course, x() can't be called unless foo is constructed successfully, but my style checker apparently hasn't figured that out.

So I'm at a loss for how to deal with this. Should I ignore the warning? Is there a way to mark it as such, so I don't get a warning anymore? Am I doing this wrong? Should I pass my reference in a different manner?

I know there are a lot of "how do I avoid this warning" questions, but it looks like mine is the first specific to JavaScript. In this case, I want to reference the thing I'm initializing inside its own declaration, like so:

var foo = new Foo({
  bar: new Bar({
    x: function(){
      doStuff(foo);
    }
  });
});

(If this looks familiar, maybe you've used ExtJS before -- this is how most of their stuff is built.)

When I call foo.bar.x(), I want to point back to the Foo (foo) that owns the Bar (bar) that's calling the function (x). This works, but my Eclipse warns me that "foo may not have been initialized", referencing the call to doStuff(); -- because, when the engine first sees the line, we haven't finished defining foo yet. Of course, x() can't be called unless foo is constructed successfully, but my style checker apparently hasn't figured that out.

So I'm at a loss for how to deal with this. Should I ignore the warning? Is there a way to mark it as such, so I don't get a warning anymore? Am I doing this wrong? Should I pass my reference in a different manner?

• javascript
• eclipse
• warnings

Share Improve this question Follow edited Oct 27, 2011 at 22:05 Coderer asked Oct 27, 2011 at 21:54 CodererCoderer 27.4k3030 gold badges104104 silver badges168168 bronze badges 2

• 1 Is that a typo? Should it be doStuff(foo) instead of doStuff(f) – Duncan Smart Commented Oct 27, 2011 at 22:00
• Don't use eclipse. There are better IDEs (WebStorm 3) – Raynos Commented Oct 27, 2011 at 22:44

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 2

var Foo = function() { }

var Bar = function (obj) {
  // foo is not initialized
  obj.x();
  // called doStuff with undefined
}

var foo = new Foo({
  bar: new Bar({
    x: function(){
      doStuff(foo);
    }
  });
});

Eclipse is right. Again if you want a better analysis system consider using WebStorm 3.0 or Visual Studio 11 as your JS IDE.

It's nothing to do with javascript, but probably something to do with Eclipse. The variable foo can be declared anywhere, since variable declarations are processed before any code is executed. It can also be initialised at any time before doStuff is called (though initialising variables without declaring them is considered bad form).

First, a Foo is constructed. To its constructor, a new Bar is passed, which is passed a function using a variable foo.

But foo is only assigned a value after the constructor of Foo is finished. At that point, the function is already declared, using the undeclared variable foo. If the function is used in the constructor of either Bar or Foo, it will fail.

I think @RobG is right, that this is an Eclipse issue and it's probably best just to deal with it. But if you wanted to avoid it, you can declare foo before you initialize it, and I bet this will keep Eclipse from plaining:

var foo;
foo = new Foo({
  bar: new Bar({
    x: function(){
      doStuff(foo);
    }
  });
});