Jquery determines whether an ID exists

Search and processing in jquery

1. Determine whether the object has a http://s.click.taobao.com/t_8? E = 7hz5x % 2bozdswsvvyc5jts79au1q % 3d % 3d & P = mm_24156262_0_0

If the following jqueryCodeIt is unavailable to determine whether an object exists.

 
If ($ ("# ID ")){
} Else {}
 

Because $ ("# ID") returns an object regardless of whether the object exists.

Correct use:

 
If ($ ("# ID"). length> 0) {} else {}
 

Use the Length attribute of the jquery object to determine whether it exists if it is greater than 0.

Or

If ($ ("# ID") [0]) {} else {}

 
Or you can directly use the native JavaScript code to determine:
 
If (document. getelementbyid ("ID") {} else {}
 
2. Search for Child Nodes Based on the parent node
 Jquery children () returns the byte point of the matched object
Children () returns the Child point of the matched object. 
<P> one </P>
<Div id = "ch">
<Span> two </span>
</Div>
Jquery code and functions:
Function JQ (){
Alert({{ch}}.children({.html ());
}
$ ("# Ch"). Children (). The result of the object [<span> two </span>. .html () is "two"

  3. Find the parent node based on the child node 
  
 
    
    
 
     
     
 
      two 
       
     
  three  
     
 
    
    
 
 
 
 jquery code and functions 
 jquery. ready ({
 alert(({{ch}}.children(??sp=}.html (); 
}); 
$ ("# Ch "). obtain the object [ two   three ] From children (). 
 $ ("# Ch "). [ three ] 
 
 
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