HTML text input allow only numeric input – Dev

The best answers to the question “HTML text input allow only numeric input” in the category Dev.

QUESTION:

Is there a quick way to set an HTML text input (<input type=text />) to only allow numeric keystrokes (plus ‘.’)?

ANSWER:

Use this DOM

<input type="text" onkeypress="validate(event)" />

And this script

function validate(evt) {
  var theEvent = evt || window.event;

  // Handle paste
  if (theEvent.type === 'paste') {
      key = event.clipboardData.getData('text/plain');
  } else {
  // Handle key press
      var key = theEvent.keyCode || theEvent.which;
      key = String.fromCharCode(key);
  }
  var regex = /[0-9]|\./;
  if( !regex.test(key) ) {
    theEvent.returnValue = false;
    if(theEvent.preventDefault) theEvent.preventDefault();
  }
}

ANSWER:

Note: This is an updated answer. Comments below refer to an old version which messed around with keycodes.

JavaScript

Try it yourself on JSFiddle.

You can filter the input values of a text <input> with the following setInputFilter function (supports Copy+Paste, Drag+Drop, keyboard shortcuts, context menu operations, non-typeable keys, the caret position, different keyboard layouts, and all browsers since IE 9):

// Restricts input for the given textbox to the given inputFilter function.
function setInputFilter(textbox, inputFilter) {
  ["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
    textbox.addEventListener(event, function() {
      if (inputFilter(this.value)) {
        this.oldValue = this.value;
        this.oldSelectionStart = this.selectionStart;
        this.oldSelectionEnd = this.selectionEnd;
      } else if (this.hasOwnProperty("oldValue")) {
        this.value = this.oldValue;
        this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
      } else {
        this.value = "";
      }
    });
  });
}

You can now use the setInputFilter function to install an input filter:

setInputFilter(document.getElementById("myTextBox"), function(value) {
  return /^\d*\.?\d*$/.test(value); // Allow digits and '.' only, using a RegExp
});

See the JSFiddle demo for more input filter examples. Also note that you still must do server side validation!

TypeScript

Here is a TypeScript version of this.

function setInputFilter(textbox: Element, inputFilter: (value: string) => boolean): void {
    ["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
        textbox.addEventListener(event, function(this: (HTMLInputElement | HTMLTextAreaElement) & {oldValue: string; oldSelectionStart: number | null, oldSelectionEnd: number | null}) {
            if (inputFilter(this.value)) {
                this.oldValue = this.value;
                this.oldSelectionStart = this.selectionStart;
                this.oldSelectionEnd = this.selectionEnd;
            } else if (Object.prototype.hasOwnProperty.call(this, 'oldValue')) {
                this.value = this.oldValue;
                if (this.oldSelectionStart !== null &&
                    this.oldSelectionEnd !== null) {
                    this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
                }
            } else {
                this.value = "";
            }
        });
    });
}

jQuery

There is also a jQuery version of this. See this answer.

HTML 5

HTML 5 has a native solution with <input type="number"> (see the specification), but note that browser support varies:

  • Most browsers will only validate the input when submitting the form, and not when typing.
  • Most mobile browsers don’t support the step, min and max attributes.
  • Chrome (version 71.0.3578.98) still allows the user to enter the characters e and E into the field. Also see this question.
  • Firefox (version 64.0) and Edge (EdgeHTML version 17.17134) still allow the user to enter any text into the field.

Try it yourself on w3schools.com.

ANSWER:

I’ve searched long and hard for a good answer to this, and we desperately need <input type="number", but short of that, these 2 are the most concise ways I could come up with:

<input type="text" 
       onkeyup="this.value=this.value.replace(/[^\d]/,'')">

If you dislike the non-accepted character showing for a split-second before being erased, the method below is my solution. Note the numerous additional conditions, this is to avoid disabling all sorts of navigation and hotkeys. If anyone knows how to compactify this, let us know!

<input type="text" 
onkeydown="return ( event.ctrlKey || event.altKey 
                    || (47<event.keyCode && event.keyCode<58 && event.shiftKey==false) 
                    || (95<event.keyCode && event.keyCode<106)
                    || (event.keyCode==8) || (event.keyCode==9) 
                    || (event.keyCode>34 && event.keyCode<40) 
                    || (event.keyCode==46) )">

ANSWER:

Here is a simple one which allows for exactly one decimal, but no more:

<input type="text" oninput="this.value = this.value.replace(/[^0-9.]/g, '').replace(/(\..*?)\..*/g, '$1');" />