Is is possible to bind a submit() function before any existing onsubmit/submit?_问答_开发者

Is is possible to bind a submit() function before any existing onsubmit/submit?

开发者 https://www.devze.com 2022-12-16 08:22 出处：网络

I have a form with an onsubmit attribute. I need to bind a new submit event and I need this one to be executed before any existing submit functions.

I have a form with an onsubmit attribute. I need to bind a new submit event and I need this one to be executed before any existing submit functions.

The following code demonstrates the problem.

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Test</title>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
    <script type="text/javascript">
      jQuery(function($) {
        // a plugin
        $('form').submit(function() {
          alert("Second");
        });
        // an other plugin
        $('form').submit(function() {
          alert("Third");
        });

        // this event must always be executed as first event
        $('form').submit(function() {
          alert("Always First");
        });
      });
    </script>
  </head>
  <body>
    <form onsubmit="javascript:alert('Fourth');">
      <p>
        <input type="submit">
      </p>
    </form>
  </body>
</html>

If yo开发者_如何学编程u execute the script, first you get "Second", then "First".

Is is possible to bind a new submit event and specify whether the function must be called before any existing event?

Constraints:

Existing events must be preserved.
I can't remove existing events because the content of the onsubmit attribute contains a quite complex logic written by Rails
(ADDED): the event should always be executed before any existing onsubmit event and already binded events (perhaps binded by an other plugin)

Any idea?

The inline submit event fires first, you could get a reference to it, nullify the onsubmit attribute on the form element, and then bind your new submit event, this one will execute your old submit handler:

  jQuery(function($) {
    var form = $('form'), oldSubmit = form[0].onsubmit;
    form[0].onsubmit = null;

    $('form').submit(function() {
      alert("First");
      oldSubmit.call(this); // preserve the context
    });
  });

Note that I use the call method to invoke your old submit handler, this is to preserve the this keyword inside that function, it will be the form element itself.

If your original onsubmit handler has some validation behavior, you can get its return value by var ret = oldSubmit.call(this);

Check the above example here.

Take the existing submit handler and store it in a variable.

Then in your new handler, call that function that you stored from the previous submit handler, and re-assign your new one to the listener.

Example:

  jQuery(function($) {

    $('form').submit(function() {
         var first = this.onsubmit;
         //...
         first.call( this );
    });
  });

...or something like that. :=)

I think this is a better way if it works which it should because the OP has accepted it.