jquery determines whether the node exists

The method for jquery to determine whether a node exists: first add an exist method to the jquery prototype; then determine the length attribute of the current object within the method; and finally use "$('#id').exist()" Just call it.

The operating environment of this tutorial: windows7 system, jquery1.10.0 version, thinkpad t480 computer.

Recommended: "jquery video tutorial" "javascript basic tutorial"

jQuery determines whether the DOM node exists in the page

1. First add an exist method to the jquery prototype;

2. Then determine within the method whether the length property of the current object is greater than 0. If it is greater than 0, it exists;

3. Finally, use $(' Just call #id').exist().

Add prototype:

(function($) {
 $.fn.exist = function(){ 
  if($(this).length>=1){
   return true;
  }
  return false;
 };
})(jQuery);

Usage method:

If the page has the following DOM nodes

<div id="a">这里是id=a节点</div>
<div>这里是DIV节点</div>
<div>这里是DIV节点</div>
<span>这里是span节点</span>

Judgement:

alert($( '#aaa').exist()); // false

alert($('#a').exist()); // true

alert($('div ').exist()); // true

alert($('p').exist()); // false

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