How to allow only digits to be entered into an input[type="number"] field?

Question

I have an input field in which the user should only be able to enter digits [0-9].

document.getElementById("integer").addEventListener('input', restrictToInteger);
function restrictToInteger() {
    this.value = this.value.replace(/[^\d]/g, '');
}

<input type="number" id="integer" />

jsFiddle Demo

The problem is this: When I enter a number (eg. 1234) and then press dot (.), + or - the content of the input field is automatically deleted by the browser (value is set to "" = empty string). But why? Changing the type from number to text seems to fix the problem. But then I lose the up/down arrow functionality of the input field. Any ideas?

Answer 1

HTML 4 has an event called onkeypress. With that attribute we can do this without using additional JS:

<input type="number" onkeypress="return (event.charCode == 8 || event.charCode == 0 || event.charCode == 13) ? null : event.charCode >= 48 && event.charCode <= 57">

Here digits from 0 to 9 are allowed using the event.charCode from 48 to 57.

Answer 2

I think the reason that the browser clean the input value it is because a string with two dots it is not a number.

Some corrections about your code:

You need to change your expression regular if you want to accept number with decimal part. Now, you are only express that you want to accept digits [0-9] and no more chars.

To accomplish want you want, you need to change /[^\d]/g to /[^\d.]/g.

document.getElementById("integer").addEventListener('input', restrictToInteger);

function restrictToInteger()
{
  this.value = this.value.replace(/[^\d.]/g, '');
}

<input type="number" id="integer" />

HOWEVER: If you define your input as number type, the regular expression is not needed. So, you just need to define the input like this and should your to your case:

<input type="number" id="integer" />

[THE SOLUTION]

To fully meet your needs, I came with a solution that catch the keydown event of the input and check if there is any '.' on the input. If yes, I prevent the char to go to the input.

document.getElementById("integer").addEventListener('keydown', restrictToInteger);
var lastCodeWasDot = false;
function restrictToInteger(e)
{
   var inputValue = document.getElementById("integer").value;
   var isDot = false;
   var isDot = (e.keyCode && e.keyCode == 110) || (e.charCode && e.charCode == 190);
   console.log(e.keyCode);
   if(isDot && (inputValue.indexOf(".") > -1 || inputValue == "" || lastCodeWasDot)) {
       e.preventDefault();
   }
   lastCodeWasDot = isDot;
   
}

<input type="number" id="integer" />

Explaning the solution:

The line of code var isDot = (e.keyCode && e.keyCode == 110) || (e.charCode && e.keyCode == 190) || false; is needed because cross browser compatibility.

I don't now why but if you try to get the value from an input number type in the firefox, and if the value finishes with a dot, the value that you will get will be without the last dot of the input. To fix that, I needed to add the variable lastCodeWasDot to fix this issue.

NOTE: The number input can accept floating point numbers, including negative symbols and the e or E character (check out this post)

Answer 3

Based on the answers of Alexandru-Ionut Mihai and natchiketa I created the following solution:

document.getElementById("integer").addEventListener("input", allowOnlyDigits);

function allowOnlyDigits() {  
  if (this.validity.valid) {
    this.setAttribute('current-value', this.value.replace(/[^\d]/g, ""));
  }
  this.value = this.getAttribute('current-value');
}

<input type="number" id="integer" />

On input the value is checked for validity. If it is valid, all non-digits are removed and the value is stored in a custom attribute of the element. If the value is not valid, the previous value is restored.

Notes:

• The RegEx-replace is required only for Internet Explorer as it allows you to enter , or . at the end of a number.
• Tested in IE, Edge, Chrome and Firefox
• Chrome still allows you to enter a + before and one , after the number.
• I found one issue: If you initialize the field with a value, the value is lost when you first hit an invalid char on the keyboard.
• Another issue: You can't enter a negative number.

Answer 4

The only problem was your input type. Change it to text and it should work !

function validate(e) {
    var charCode = e.keyCode? e.keyCode : e.charCode
    if (!(charCode >= 48 && charCode <= 57)) {
        if(!(charCode>=37 && charCode<=40))
            if(charCode!=8 && charCode!=46)
            return false;
    }
}

<input type="number" id="integer" pattern="[0-9]"
onkeydown="return validate(event)"/>

Answer 5

You can achieve your requirement by copying the old value of input and using setAttribute and getAttribute methods in order to store the values.

function myFunction(input){
  input.setAttribute('current-value',"");
  input.oninput=function(){  
      let currentValue=input.getAttribute('current-value');
      if(input.value!='' || (currentValue>=1 && currentValue<=9))
        input.setAttribute('current-value',input.value);
      input.value=input.getAttribute('current-value');
  }
}

<input type="number" oninput="myFunction(this)"/>
<input type="number" oninput="myFunction(this)"/>
<input type="number" oninput="myFunction(this)"/>
<input type="number" oninput="myFunction(this)"/>
<input type="number" oninput="myFunction(this)"/>

Answer 6

I would switch to a cancelable event like keydown.
That way you can prevent the character from being typed in the first place:

var cancelEvent = function (e) {
    e.preventDefault();
    return false;
},
restrictToInteger = function restrictToInteger(e) {
    var acceptableInput = /[0-9]/g,
        clipboardKeys = /[zxcv]/ig,
        field = e.key || e.char,
      isClipboardOperation = (clipboardKeys.test(field) && e.ctrlKey),
        inputIsAcceptable = field ? (
            acceptableInput.test(field)
            || field.length > 1
            || isClipboardOperation
        ) : true;

    if (!inputIsAcceptable) {
        cancelEvent(e);
    }
},
ensureIntegerValueOnPaste = function ensureIntegerValueOnPaste(e) {
 var data = e.clipboardData || e.dataTransfer,
    text = data.getData('text'),
        int = parseInt(this.value + text, 10);

    if (isNaN(int)) {
        cancelEvent(e);
    } else {
        window.setTimeout(function () {
            e.target.value = int;
        }, 0);
    }
},
input = document.getElementById("integer");

input.addEventListener('keydown', restrictToInteger);
input.addEventListener('drop', ensureIntegerValueOnPaste);
input.addEventListener('paste', ensureIntegerValueOnPaste);

<input type="number" id="integer" />

Updated fiddle: https://jsfiddle.net/838pa8hv/2/

Disclaimers:

• Only tested in Chrome.
• The test for field.length > 1 is to catch non-numeric keys that are valid as the up/down arrows have a value of ArrowUp and ArrowDown respectively. This also allows for keys like Shift (or Home, Backspace, Delete, etc.) to be pressed as well.

Edit: To handle pastes (and drops), you can do the same thing in those respective events. Updated fiddle and code snippet above.

Edit:
If the expected usability is to be able to paste/drop partial numbers into the field and to not allow negative integers, then you can just change how int is defined in the ensureIntegerValueOnPaste function. Updated fiddle and code snippet above.

Answer 7

When you call oninput, the <input> element first calls its internal methods to handle the value. This prevents your function from seeing any actual erroneous characters, namely e+-. - all used by JavaScript to format numbers.

You can see this by adding console.log calls before and after changing this.value.

console.log(this.value);
this.value=this.value.replace(/[^\d]/g, '');
console.log(this.value);

There is never any difference!

If you try, for example:

console.log(this.value);
this.value+=1; // or *=2 for numerical fun
console.log(this.value);

you can see a difference.

So your function is hastening the normal internal calls <input type='number'/> would normally make when handling illegal input.

Can't quite see why the field is left blank and not 1 though.

Answer 8

You don't need regular expression, you can use parseFloat() function. Your input type remains unchanged, there are still "arrows" to increase/decrease number and also it makes sure that your input will not start with zero.

document.getElementById("integer").addEventListener('input', restrictToInteger);
function restrictToInteger() {
  this.value = parseFloat(this.value);
}

<input type="number" id="integer" />

Answer 9

You have to check if the value is not a number and then stop user.

document.getElementById("integer").addEventListener('input', restrictToInteger);

function restrictToInteger(e)
{
  if(isNaN(e.data)){
     alert("only numbers allowed");
  }
}

<input type="number" id="integer" />