How can I get jquery .val() AFTER keypress event?

问题:

I got:

$(someTextInputField).keypress(function() {
  alert($(this).val());
});

Now the alert always returns the value BEFORE the keypress (e.g. the field is empty, I type 'a' and the alert gives me ''. Then I type 'b' and the alert gives me 'a'...). But I want the value AFTER the keypress - how can I do that?

Background: I'd like to enable a button as soon as the text field contains at least one character. So I run this test on every keypress event, but using the returned val() the result is always one step behind. Using the change() event is not an option for me because then the button is disabled until you leave the text box. If there's a better way to do that, I'm glad to hear it!

回答1:

Change keypress to keyup:

$(someTextInputField).on("keyup", function() {
  alert($(this).val());
});

keypress is fired when the key is pressed down, keyup is fired when the key is released.

回答2:

Surprised that no one mentioned the js "input" event:

$(someTextInputField).on('input', function() {
  alert($(this).val());
});

Recommended.

https://developer.mozilla.org/en-US/docs/Web/Events/input

回答3:

instead of keypress, use keyup.

回答4:

Alternatively, you can use the keydown event with a timeout of 0.

That way, the changes will be applied instantly, instead of being applied when the user stops holding the key.

$(someTextInputField).on("keydown", function() {
  setTimeout(function($elem){
    alert($elem.val());
  }, 0, $(this));
});

回答5:

You may want to hook up an onchange event handler instead of using any of the key events.

$(someTextInputField).change(function() {
    alert($(this).val());
});

Using Edit > Paste or a Right-Click then Paste will fire a change event, but not a key event. Note some browsers may simulate a key event on a paste (though I don't know of any) but you can't count on that behavior.

回答6:

Try something like this:

$('#someField').keypress(function() {
  setTimeout(function() {
    if ($('#someField').val().length > 0)
      $('#theButton').attr('disabled', false);
  }, 1);
});

That simply introduces a timeout so that after the "keypress" event loop completes, your code will run almost immediately thereafter. Such a short timer interval (even if rounded up by the browser) will not be noticeable.

edit — or you could use "keyup" like everybody else says, though its semantics are different.