OK, Javascript gurus, why is "if" not evaluating as true or false ?

Marc Clifton

For example:

            // Wow, more stupid Javascript.  We can't just do this:
            // return ($(e.target).parents('.jqx-tree').length > 0)

            // We actually have to do this.  WTF?
            if ($(e.target).parents('.jqx-tree').length > 0) {
                return false;
            }
            return true;

WTF is the reason I can't just do a return on > comparison??? Marc

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Richard Deeming

I can't reproduce the problem. Given:

var result = $(" ... ").length > 0;
alert(typeof result);
alert(result);

the code displays "boolean" and "true". What output do you get if you try:

var result = ($(e.target).parents('.jqx-tree').length > 0);
alert(typeof result);
alert(result);
return result;

As a last resort, there's always the "!!" trick to convert to a boolean value:

return !!($(e.target).parents('.jqx-tree').length > 0);

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Marc Clifton

Yeah, it looked like a boolean to me too! !! didn't work, but SO provided what I think is a better solution anyways:

    function disableBrowserContextMenu() {
        $(document).on('contextmenu', function (e) {
            if ($(e.target).parents('.jqx-tree').length > 0) {
                e.preventDefault()
            }
        });
    }

Note the e.preventDefault(). Somehow, the explicit return true/false must have been doing this behind the scenes, I'm wildly guessing. Marc

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Richard Deeming

In jQuery event handlers, return false; should be directly equivalent to e.preventDefault(); e.stopPropagation();, and usually works to cancel an event. Having said that, e.preventDefault() is the preferred way to stop the event. The difference between ‘return false;’ and ‘e.preventDefault();’[^] jQuery Events: Stop (Mis)Using Return False[^]

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Marc Clifton

Richard Deeming wrote:

In jQuery event handlers,

Heh, this is what happens when a noob (which I still consider myself) starts doing Javascript. Good to know, and thank you for the great info! Marc

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Afzaal Ahmad Zeeshan

I didn't know that !! operator. Thanks. ;-) Removed irrelevant content

The shit I complain about It's like there ain't a cloud in the sky and it's raining out - Eminem ~! Firewall !~

F ES Sitecore

To take a stab at the original question, jquery functions always return collections which is why a) can chain things b) never have to check for nulls. If $(e.target) returned a single thing and parents('.jqx-tree') returned a single thing then your code would make sense and work. But you actually have a foreach loop acting on a foreach loop...the first $() returns a collection (even if that collection only has one item) and the .parents works on each item in that collection and returns its own collection which your .length acts on. Now imaging $(..) returns 3 items (a, b and c) and the .parents of each of those items returns 1,0 and 5 items. a.parents.length = 1 b.parents.length = 0 c.parents.length = 5 now your code

if ($(e.target).parents('.jqx-tree').length > 0)

makes less sense, which "length" are you evaluating? This idea about returning collections is probably what is stopping your code from working how you would expect. Maybe :) someone might know better.

Richard Deeming

But e.target will be a single DOM element, so $(e.target) will be a jQuery wrapper containing a single element. And even if it contained three elements, the .parents(...) call would return a jQuery wrapper containing the matching parents of all three elements. So in your example, the .length property would return 6.

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

F ES Sitecore

Richard Deeming wrote:

But e.target will be a single DOM element, so $(e.target) will be a jQuery wrapper containing a single element.

It will be a collection that contains a single element. new string[]{"hello"} is not interchangeable with "hello" Like I said, I don't know js well enough to know if this is the reason that the original code isn't working as intended, I'm just saying it might be a possible reason.

Richard Deeming

All jQuery wrapper objects are collections, whether they contain multiple elements, a single element, or no elements.

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

F ES Sitecore

Yes, that's what I'm saying :)