I am a jQuery beginner and while going through some code examples I found:
$(document.body) and $('body')
Is there any difference between these two?
This question is related to
jquery
document
document-body
The answers here are not actually completely correct. Close, but there's an edge case.
The difference is that $('body') actually selects the element by the tag name, whereas document.body references the direct object on the document.
That means if you (or a rogue script) overwrites the document.body element (shame!) $('body') will still work, but $(document.body) will not. So by definition they're not equivalent.
I'd venture to guess there are other edge cases (such as globally id'ed elements in IE) that would also trigger what amounts to an overwritten body element on the document object, and the same situation would apply.
$(document.body) is using the global reference document to get a reference to the body, whereas $('body') is a selector in which jQuery will get the reference to the <body> element on the document.
No major difference that I can see, not any noticeable performance gain from one to the other.
They refer to the same element, the difference is that when you say document.body you are passing the element directly to jQuery. Alternatively, when you pass the string 'body', the jQuery selector engine has to interpret the string to figure out what element(s) it refers to.
In practice either will get the job done.
If you are interested, there is more information in the documentation for the jQuery function.
I have found a pretty big difference in timing when testing in my browser.
I used the following script:
WARNING: running this will freeze your browser a bit, might even crash it.
var n = 10000000, i;_x000D_
i = n;_x000D_
console.time('selector');_x000D_
while (i --> 0){_x000D_
$("body");_x000D_
}_x000D_
_x000D_
console.timeEnd('selector');_x000D_
_x000D_
i = n;_x000D_
console.time('element');_x000D_
while (i --> 0){_x000D_
$(document.body);_x000D_
}_x000D_
_x000D_
console.timeEnd('element');<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>I did 10 million interactions, and those were the results (Chrome 65):
selector: 19591.97509765625ms
element: 4947.8759765625ms
Passing the element directly is around 4 times faster than passing the selector.
Outputwise both are equivalent. Though the second expression goes through a top down lookup from the DOM root. You might want to avoid the additional overhead (however minuscule it may be) if you already have document.body object in hand for JQuery to wrap over. See http://api.jquery.com/jQuery/ #Selector Context
There should be no difference at all maybe the first is a little more performant but i think it's trivial ( you shouldn't worry about this, really ).
With both you wrap the <body> tag in a jQuery object
Source: Stackoverflow.com