jquery Ajax has not waited until the success callback to brush off, entered the ONERROR function error case analysis

jquery Ajax has not yet waited for the success callback to be brushed off, into the OnError function error case analysis :

The same request was requested at the same time 2 times, and then the second request to brush off the first time!

(Example: <div onclick= "ajax (URL)" ><a onclick= "Ajax (URL)" > Get Interface Data </a></div>) clicking "Get Interface Data" will trigger the function Ajax (URL) 2 times! That's a problem!

For example, if the shopping cart "add to the Shopping cart" button-style so designed, then each click on the shopping cart, will add two products to the shopping cart!

For example, <input type= "Submit" name= "submit" value= "Login" tabindex= "5"/> To bind the onclick event will be repeated with the form submit!