如何从匿名函数获取值？

Question

Here is the code and fiddle :

var test = function(){
    return{
        value: "hi",
        func1: function(){
            func2();
        }()
    };
}();

function func2(){
    alert(test.value);
}

Can anyone tell me what have I done wrong? I can't get test.value.

Answer 1

Your func2() is called from the IIFE for the func1 property in the IIFE that constructs the object to be assigned to test . Before it assigns to test . And it tries to access the test.value property, on a variable that is yet undefined , and throws a ReferenceError therefore. (See also Self-references in object literal declarations )

I think you are looking for

var test = function(){
    return{
        value: "hi",
        func1: function(){
            func2();
        } // <-- no invocation here, make `func1` a method not `undefined`
    };
}();

function func2(){
    alert(test.value);
}

test.func1(); // "hi"

( updated fiddle )

Answer 2

If you run this code you'll be getting an undefined . Why? Well because you haven't given enough time for your test to actually initiate itself ( and the fact that what you're doing this in a synchronous way).

Try this asynchronous solution.

var test = function(){
    return{
        value: "hi",
        func1: function(){
            setTimeout(function(){ func2(); }, 50);
          //you can also just do
          //setTimeout(func2, 50);
        }()
    };
}();

function func2(){
    alert(test.value);
}

Demo

Also notice that you don't return anything to your func1 since it auto invoques itself. Later on if you try to do test.func1() it won't work.

Answer 3

The problem is that you assign an object literal to test . However, to build that object, you call func2 . That function attempts to access test , but at that point it still is undefined.

Therefore, you should call func2 after assigning the object to test :

var test = function(){
    return {
        value: "hi",
    };
}();
test.func1 = function(){
    func2();
}();
function func2(){
    alert(test.value);
}

However, note that's a bit weird, because the anonymous function doesn't return any value. func2(); test.func1 = undefined func2(); test.func1 = undefined would be more natural.

Answer 4

As Bergi mentioned you want to use Imidiatelly Invoked Function Expression (IIFE) but your syntax is wrong.

see fixed fiddle

var test = (function(){
    return{
        value: "hi",
        func1: function(){
            func2();
        }
    };
})();

function func2(){
    alert(test.value);
}

With ( at the start of your function and at the end of it before you actually immediately call it