jQuery检测已经渲染的元素？

Question

I need write some function which will be detect any jquery selector: already exists in DOM or not. How i can do that.

If element rendered it must return true, if element not rendered it must return false.

Possible selectors:

'<div />'  // text jquery selected will converted to $('<div />') 
$('<div />') // simple jquery selector such as jQuery('<div />')
'#somediv' or .somediv // already rendered DOM element

isDomExists('<div />') => false

isDomExists($('<div />')) => false

isDomExists($('#somediv')) => true

Answer 1

This will return true for elements that are currently in the document, and selectors which match elements in the document.

function isInDoc(sel) {
    var $sel = jQuery(sel);
    return $sel.length && jQuery.contains(document.documentElement, $sel[0]);
}

Answer 2

You can also check the number of parents of the node, nodes with no parent is not contained in the DOM :

http://jsfiddle.net/w6XZZ/

HTML:

<div id="mydiv"></div>

Javascript :

alert($("<div/>").parent().length);
alert($("#mydiv").parent().length);

Answer 3

$('<div />') creates a new DIV element (but does not append to the DOM). What you need instead is $('div').length == 0

Answer 4

您可以只使用jquerys .ready() ： 文档