Question

I have a function, say:

function some_name( that ) {
// do something here
}

This function gets called in 2 places. Place 1 is at document.ready and place 2 is when a button is clicked.

So:

// document.ready
function some_name();

...

// button click
function some_name( $(this) );

Now going back to the function itself, how do I check if that has been set?

Answer 1

One option is using typeof:

function some_name(that) {
    if (typeof that != "undefined") {
        // do smth with that
    } else {
        // do smth without that
    }
}

Another option is using arguments:

function some_name(that) {
    if (arguments.length) {
        // do smth with that
    } else {
        // do smth without that
    }
}

---

If you also need to check if element $(this) exists on a page, you can use length:

if (that.length) {
    // element exists
} else {
    // element does not exist
}