Detect backspace and del on "input" event?

Question

How to do that?

I tried:

var key = event.which || event.keyCode || event.charCode;

if(key == 8) alert('backspace');

but it doesn't work...

If I do the same on the keypress event it works, but I don't want to use keypress because it outputs the typed character in my input field. I need to be able to control that

---

my code:

  $('#content').bind('input', function(event){

    var text = $(this).val(),
        key = event.which || event.keyCode || event.charCode;

    if(key == 8){
      // here I want to ignore backspace and del
    }

    // here I'm doing my stuff
    var new_text = 'bla bla'+text;
    $(this).val(new_text);
  });

no character should be appended in my input, besides what I'm adding with val() actually the input from the user should be completely ignored, only the key pressing action is important to me

Answer 1

Use .onkeydown and cancel the removing with return false;. Like this:

var input = document.getElementById('myInput');

input.onkeydown = function() {
    var key = event.keyCode || event.charCode;

    if( key == 8 || key == 46 )
        return false;
};

---

Or with jQuery, because you added a jQuery tag to your question:

jQuery(function($) {
  var input = $('#myInput');
  input.on('keydown', function() {
    var key = event.keyCode || event.charCode;

    if( key == 8 || key == 46 )
        return false;
  });
});

​

Answer 2

event.key === "Backspace"

More recent and much cleaner: use event.key. No more arbitrary number codes!

input.addEventListener('keydown', function(event) {
    const key = event.key; // const {key} = event; ES6+
    if (key === "Backspace" || key === "Delete") {
        return false;
    }
});

Mozilla Docs

Supported Browsers

Answer 3

With jQuery

The event.which property normalizes event.keyCode and event.charCode. It is recommended to watch event.which for keyboard key input.

http://api.jquery.com/event.which/

jQuery('#input').on('keydown', function(e) {
    if( e.which == 8 || e.which == 46 ) return false;
});

Answer 4

It's an old question, but if you wanted to catch a backspace event on input, and not keydown, keypress, or keyup—as I've noticed any one of these break certain functions I've written and cause awkward delays with automated text formatting—you can catch a backspace using inputType:

document.getElementsByTagName('input')[0].addEventListener('input', function(e) {
    if (e.inputType == "deleteContentBackward") {
        // your code here
    }
});

Answer 5

keydown with event.key === "Backspace" or "Delete"

More recent and much cleaner: use event.key. No more arbitrary number codes!

input.addEventListener('keydown', function(event) {
    const key = event.key; // const {key} = event; ES6+
    if (key === "Backspace" || key === "Delete") {
        return false;
    }
});

Modern style:

input.addEventListener('keydown', ({key}) => {
    if (["Backspace", "Delete"].includes(key)) {
        return false
    }
})

Mozilla Docs

Supported Browsers

Answer 6

Have you tried using 'onkeydown'? This is the event you are looking for.

It operates before the input is inserted and allows you to cancel char input.

Answer 7

$('div[contenteditable]').keydown(function(e) {
// trap the return key being pressed
if (e.keyCode === 13 || e.keyCode === 8)
{
    return false;
}
});

Answer 8

on android devices using chrome we can't detect a backspace. You can use workaround for it:

var oldInput = '',
    newInput = '';

 $("#ID").keyup(function () {
  newInput = $('#ID').val();
   if(newInput.length < oldInput.length){
      //backspace pressed
   }
   oldInput = newInput;
 })

Answer 9

InputEvent.inputType can be used for Backspace detection Mozilla Docs. It works on Chrome desktop, Chrome Android and Safari iOS.

<input type="text" id="test" />

<script>  
  document.getElementById("test").addEventListener('input', (event) => {
  console.log(event.inputType);
  // Typing of any character event.inputType = 'insertText'
  // Backspace button event.inputType = 'deleteContentBackward'
  // Delete button event.inputType = 'deleteContentForward'
  })
</script>

Answer 10

//Here's one example, not sure what your application is but here is a relevant and likely application 
function addDashesOnKeyUp()
{
    var tb = document.getElementById("tb1"); 
    var key = event.which || event.keyCode || event.charCode;

    if((tb.value.length ==3 || tb.value.length ==7 )&& (key !=8) ) 
    {
        tb.value += "-"
    } 
}

Answer 11

Live demo

Javascript
<br>
<input id="input">
<br>
or
<br>
jquery
<br>
<input id="inpu">

<script type="text/javascript">
var myinput = document.getElementById('input');
input.onkeydown = function() {
  if (event.keyCode == 8) {
    alert('you pressed backspace');
    //event.preventDefault(); remove // to prevent backspace
  }

  if (event.keyCode == 46) {
    alert('you pressed delete');
    //event.preventDefault(); remove // to prevent delete
  }
};

//jquery code

$('#inpu').on('keydown', function(e) {
  if (event.which == 8) {
    alert('you pressed backspace');
    //event.preventDefault(); remove // to prevent backspace
  }

  if (event.which == 46) {
    alert('you pressed delete');
    //event.preventDefault(); remove // to prevent delete
  }
});
</script>