Question

I have a 3rd party JavaScript application that declares several global functions and needs some variables to be defined for those functions to work. I would rather not define those variables in the global scope. Here’s an example:

Suppose you have a globally defined function foo that prints out the value of an externally-defined variable named x.

function foo() {
    console.log(x);
}

I think the only way for x to have a value within foo is if x is also a global. I hope I’m wrong. What I would really like to do is this:

(function () {
    var x = 'someValue';
    var bar = magicallyFixSoXIsntGlobal(foo);
    bar();
}());

I guess I could do:

(function () {
    var x = 'someValue';
    var bar = Function(foo.toString());
    bar();
}());

But that seems pretty much like eval. (If it comes down to that, I’d rather have global spam than use eval.)

Is there any way to “fix” the global functions so they can refer to the enclosed values?

Answer 1

Assign a value to a window‘s property, call the function, then use the delete operator to truly remove the variable.

window.foo = 'bar';
magic();
delete window.foo; // Because `foo` is defined without `var`, it can be deleted