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bg17aw

How to use "this" in a selector expression?

in Using jQuery • 6 years ago

Can I use "this" in a selector expression? Something like

$("this > childrenelement").....

I did see here something like:

$(' > img', this)

But where is this documented/explained better?

Since "this" is a javascript keyword and not just a jQuery keyword, it would be interesting to have an answer from both jQuery and Javascript point of view.

Replies(3)

jakecigar

Re: How to use "this" in a selector expression?

6 years ago

this is a variable, not a keyword.

this gets set with every function you enter.

Some say this is evil. Others embrace this.

Millions of pages have been written about --> this, <-- read a few hundred.

Both of your lines of code are bad.

#1 does nothing.

#2 is inefficient.

Use

$(this).children("Img")

JΛ̊KE

bg17aw

Re: How to use "this" in a selector expression?

6 years ago

Yes, first line it is just something to try and show what I am trying to achieve.

Second one though, I posted the source, I would love to have someone explain what it does / how it works /why it is inefficient.

In an itteration over a collection, you might need to get the children of each of the elements in the collection.

"this" seems the way to go, unless I am missing someting.

jakecigar

Re: How to use "this" in a selector expression?

6 years ago

I use this less often these days. With most browsers supporting arrow functions, you don’t get a new this with an arrow function. f=>f+1 is an arrow function. function(f){ return f+1} is a regular/classic/standard function.

But back to this…

this is neither efficient nor inefficient. It is just a variable. It is set automatically for you. You can use it when you need it or use another way to get to where you going. Maybe a selector or event.target or a million other ways.

'> img' is inefficient. Not the this part. It is a sizzle query and not a built-in DOM query. There are many posts on the net about sizzle vs document.querySelectorAll. jQuery uses both. And it’s not so inefficient as to make any difference in a normal script.

JΛ̊KE

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