CODEWITHSUNDEEP
javascriptjquery
sam.smith
sam.smith

Reputation: 45

What does "this" stand for here?

Given the code:

$(element, document).mousedown(function() {
        $(this).attr('id'); // get id of the element

});

how to rewrite the code without using this?

Upvotes: 3

Views: 334

Answers (7)

Mark Keats
Mark Keats

Reputation: 1400

You can use the following:

$(element, document).mousedown(function(e) {
        $(e.target).attr('id'); // Get id of the element.
});

Upvotes: 1

cwallenpoole
cwallenpoole

Reputation: 81988

The problem is that you're not going to get anything more efficient than use of this. Everything else will more or less require a second element lookup which, while not deathly expensive is nevertheless more costly than using the object in scope (this).

Strictly speaking, this is the most literal interpretation:

$(element, document).mousedown(function() {
        $(element, document).attr('id'); 
});

Now, this might be OK, but if your element is actually a selector which returns multiple values (like a class selector), you'll have problems. So, instead, you might want to consider:

$(element, document).each( function( ind, elem ) {
    elem.mousedown( function(){ elem.attr( 'id' ); } );
} );

Upvotes: 0

frosty
frosty

Reputation: 21762

"this" refers to the scope of the function. With regards to the function, This is the element being acted upon. In the case of you code, the action is mousedown, so the element being acted upon is this. Hope this help.

Upvotes: 0

Coomie
Coomie

Reputation: 4868

In this case "this" is refering to the element that is being clicked. It's not required but you'll have to have code like this for every element:

$("#button").mousedown(function(){
 $("#button").attr("id");
})

It's much easier to leave it in

Upvotes: 0

Tigraine
Tigraine

Reputation: 23648

this in JavaScript stands for the execution context of a function. In this case you benefit from jQuery setting this to the element you bound things on. But with self-written functions you'll usually end up with this referring to the global object.

In case you ever enter a new function scope you usually have to preserve this because a new function has a new this.

For example

$('div').each(function(index, item) {
    var that = this;
    $(this).mousedown(function() {
        //this could be something different than before 
        //so we use the that reference
        $(that).hide();
    }
});

Upvotes: 0

Pekka
Pekka

Reputation: 449385

what is THIS stands for?

In this context, this points to the element that you are currently defining the mousedown property for.

I can't see a reason not to use it here. Can you elaborate on what you want to do?

Upvotes: 3

Simeon
Simeon

Reputation: 5579

A version without the this keyword:

var $element = $('#element');
$element.mousedown(function() {
    var id = $element.attr('id');
        // id is now 'element'
});

Upvotes: 1

Related Questions