Change value of input then submit form in JavaScri

问题:

I'm currently working on a basic form. What I want to do with this form is that when you hit submit/button to first change the value of a field and then submit the form as usual. It all looks a bit like this:

<form name="myform" id="myform" action="action.php">
<input type="hidden" name="myinput" value="0" />
<input type="text" name="message" value="" />
<input type="submit" name="submit" onclick="DoSubmit()" />
</form>

And this is how far I've come with the JavaScript. It changes "myinput"'s value to 1 but does not submit the form. I'm really a JavaScript noobie so forgive me if this is just a too simple question but I'm just not getting the hang of it really.

function DoSubmit(){
  document.myform.myinput.value = '1';
  document.getElementById("myform").submit();
}

回答1:

You could do something like this instead:

<form name="myform" action="action.php" onsubmit="DoSubmit();">
<input type="hidden" name="myinput" value="0" />
<input type="text" name="message" value="" />
<input type="submit" name="submit" />
</form>

And then modify your DoSubmit function to just return true, indicating that "it's OK, now you can submit the form" to the browser:

function DoSubmit(){
  document.myform.myinput.value = '1';
  return true;
}

EDIT: I'd also be wary of using onclick events on a submit button; the order of events isn't immediately obvious, and your callback won't get called if the user submits by, for example, hitting return in a textbox.

回答2:

document.getElementById("myform").submit();

This wont work as your form tag has no id.

Change it like this and it should work:

<form name="myform" id="myform" action="action.php">

回答3:

here is simple code , you must set an id for you input here call it 'myInput' :

      var myform = document.getElementById('myform');
      myform.onsubmit = function(){ 
                    document.getElementById('myInput').value = '1';
                    myform.submit();
                  };

回答4:

No. When your input type is submit, you should have an onsubmit event declared in the markup and then do the changes you want. Meaning, have an onsubmit defined in your form tag.

Otherwise change the input type to a button and then define an onclick event for that button.

回答5:

You're trying to access an element based on the name attribute which works for postbacks to server but javascript responds to the id attribute. Add an id with the same value as name and all should work fine.

<form name="myform" id="myform" action="action.php">
  <input type="hidden" name="myinput" id="myinput" value="0" />
  <input type="text" name="message" id="message" value="" />
  <input type="submit" name="submit" id="submit" onclick="DoSubmit()" />
</form>

function DoSubmit(){
  document.getElementById("myinput").value = '1';
  return true;
}

回答6:

My problem turned out to be that I was assigning as document.getElementById("myinput").Value = '1';

Notice the capital V in Value? Once I change it to small case ie; value, the data started posting. Odd as it was not giving any Javascript errors as well

回答7:

Can you using onchange Event

<form name="myform" id="myform" action="action.php">
<input type="hidden" name="myinput" value="0" onchange="this.form.submit()"/>
<input type="text" name="message" value="" />
<input type="submit" name="submit" onclick="DoSubmit()" />
</form>