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What does $(selector)[0] mean in jQuery?

rated 0 times [ 155] [ 5] / answers: 1 / hits: 27976 / 9 Years ago, fri, september 25, 2015, 12:00:00

The syntax that I don't understand is this:

$(#profilePhotoFileUpload)[0]

I have been seeing this syntax pretty frequently and I've ignored it for a while because I never had to use it. But now, in order to understand the code from this post How do I upload an image using the Parse.com javascriptSDK?, I cannot ignore it any longer.

I know that [0] this syntax is used to refer to an array usually. But it seems a little weird that a reference to an id would generate an array of some sort.

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kevonmoisesf

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answered 9 Years ago alorafrancisl · Accepted Answer

By appending [0] to the jQuery object will return the first DOM element.

As you're using id selector here, there will be only one element in the array so using [0] makes sense. If you are selecting multiple elements you can also use any number which is between 0 and number of elements you can get corresponding DOM element.

From jQuery Docs

A jQuery object contains a collection of Document Object Model (DOM) elements that have been created from an HTML string or selected from a document. Since jQuery methods often use CSS selectors to match elements from a document, the set of elements in a jQuery object is often called a set of matched elements or selected elements.

The jQuery object itself behaves much like an array; it has a length property and the elements in the object can be accessed by their numeric indices [0] to [length-1]. Note that a jQuery object is not actually a Javascript Array object, so it does not have all the methods of a true Array object such as join().