is there a simple way to check if given selector string point to only one element?

example

开发者_开发技巧$('div.mydiv').checkifonlyone().css('background-color', 'red');

or maybe

$('div.mydiv').filter(':checkifonlyone').css('background-color', 'red');

I expect that there is only one div with that class in document, otherwise an error msg should be displayed and script should cease to execute ?

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Could either look like:

$('div.mydiv:eq(0)').css('background-color', 'red');

That one would always select the first element if there are multiple.

or

var $mydiv = $('div.mydiv');
if($mydiv.length === 1) {
   $mydiv.css('background-color', 'red');
}

Which infact only would change the background color if there is exactly one match on the selector.

---

You can do it yourself:

if ($(something).length !== 1)
    //Waaaah!

---

var myDivs = $('div.mydiv');
if(myDivs.length === 1)
{
 myDivs.css('background-color', 'red');
}

---

if ( $('div.mydiv').length == 1 ) ....

Looking for that? Remember the jQuery element is an array of matches that are iterated by most of the functions (or a top element is popped off).

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You need size() function.

It will return numbers of elements in your selector and you can then act on that result accordingly.

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Depending on your markup, you might be able to use the :only-child selector, but you'll probably have to do something like this :

var $myDiv = $('div.mydiv');
if ($myDiv.length == 1) $myDiv.css('background-color', 'red');