javascript anonymous function parameter passing

Question

I have some javascript code (within an object) :

toggle: function() {
    var me = this;
    var handler = function() { me.progress() };
    me.intervalId = setI         


        

Answer 1

The anonymous function has access to me because it is declared inside of the outer function (the toggle function); it is closed over by the outer function.

Your handler function will be called by setInterval, which passes exactly zero arguments. This means you can't use parameters in the handler function itself.

I you really want to pass me explicitly, you could write a function accepting an parameter, and have that function return an anonymous function without parameters, but which could access the creator function's parameter:

toggle: function() {
    var me = this;
    var handler = (function (o) { return function() { o.progress() }; })(me);
    me.intervalId = setInterval(handler, me.intervalTime);
    //...More code
}

But this basically adds a layer of redirection without really making it more legible. Unless you pull that creating function outside:

function createProgressHandler(o) {
    return function() {
        o.progress();
    };
}

// ...

toggle: function() {
    var me = this;
    var handler = createProgressHandler(me);
    me.intervalId = setInterval(handler, me.intervalTime);
    //...More code
}