Joined July 2012
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A510a332dd609f34f1adb36d3235286b

Thomas Puppe

ONDIGO
ONDIGO
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Berlin
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You are totally right. I didn't see that parameter for json_decode. So as long as you know that the JSON Object has been/should be a PHP array (which is the case for my app), this is the better method.

Thank you for the hint.

@mlb You are absolutely right! Sizzle selectors are handled right-to-left.

Is this something that has changed recently? I always believed jQuery works left-to-right, and noone ever disagreed. Maybe it is because I am used to put IDs as the first operand, and have this in examples and tests as well.?

EXCEPTION: when there is an ID as the first element/operand – which is the subject of this discussion – then jQuery/Jizzle optimizes it by first selecting the ID element and then searching inside it. (At least that is what I have found.) This behaviour is like working left-to-right .

Sizzle is highly optimized and I guess they have different behaviour for different selectors and also take browser features into account.

In general, I can only repeat the advice some people already gave: Testing a certain solution onj jsperf (or similar) is always a good idea. E.g.: http://jsperf.com/specific-left-or-right

It is important to know that jQuery Selectors are handled left to right! The whole "protip" suffers from the misunderstanding that jQuery would work like CSS (right to left).

That's why the analogy with the students in room is wrong.

Doing $('a #foo'); would be searching all students and then find the students from room 123. And it would be very inefficient in the DOM.

Doing $('#foo a'); is similar to $('#foo').find('a'); and only has the performance impact od deconstructing the String "#foo a" into "#foo" and "a" (and function calls. The DOM traversion should be nearly the same.

// Update 2012-12-03:
As @mlb has said, in general, Sizzle selectors are handled right-to-left. Exception: when there is an ID as the first element/operand – which is the subject of this discussion – then jQuery/Jizzle optimizes it by first selecting the ID element and then searching inside it. (At least that is what I have found.)

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