为什么函数没有被调用并抛出错误？

Question

The below is my code

function callName() {
    var name="x";

    function printName(){
        alert(name);
    }

    return printName;
}

name = callName();
alert(name);
name();

When i execute it, the alert statement is printing the printName function perfectly, but the function call name() is giving an error stating string is not a function. if scope is the problem the alert should have printed the name instead of the function. I am trying to understand closures here and was trying this out and got confused with the scope management in js.

Answer 1

You haven't declared name in the outer scope, so it's using the global scope, and is actually pointing to window.name . Just declare it as a local variable, and you're set:

function callName() {
    var name="x";

    function printName(){
        alert(name);
    }

    return printName;
}

var name = callName();
alert(name);
name();

Since window.name is the name of the window, when you assign to it, it's assigning the string contents to the name of the window, and is still a string - that's why you can't call it with name() .

Note that this will only work if this code itself is within another scope - if it's on the global scope, even using var name won't help, as it will still conflict with the global window.name property.

Answer 2

That is because inside callName() you set the var name to string. If you do this:

var name = callName();

You will be creating a new var name different of the one inside callName() .

Fiddle