Passing arguments to an IIFE

Question

What's the correct syntax for passing arguments to an IIFE stored in a variable?

Example below tells me that foo is not defined, regardless on if I call the function or not:

var bar = (function(foo){

    return { 
        getFoo: function(){
            return foo;
        } 
    }

})(foo);

console.log(bar.getFoo(1));

http://jsfiddle.net/eSTkL/

Answer 1

The IIFE is immediately invoked. You are passing foo to it at the moment of invocation, and I suppose it's undefined.

What gets stored in bar is not the IIFE, but the object returned by the IIFE, that doesn't have anything to do with foo (beside having access to it via closure). If you want foo to be 1, don't pass that value to getFoo, but to the IIFE itself:

var bar = (function(foo){

    return { 
        getFoo: function(){
            return foo;
        } 
    }

})(1);

console.log(bar.getFoo()); // 1

If you want a getter and a setter (actually, getter/setter-like functions), use this:

var bar = (function(foo){

    return { 
        getFoo: function(){
            return foo;
        },
        setFoo: function(val) {
            foo = val;
        }
    }

})(1);

console.log(bar.getFoo()); // 1
bar.setFoo(2);
console.log(bar.getFoo()); // 2