Javascript - validation, numbers only

Question

I'm trying to get my login form to only validate if only numbers were inputted. I can it to work if the input is only digits, but when i type any characters after a number, it will still validate etc. 12akf will work. 1am will work. How can i get past this?

Part of the Login

<form name="myForm">
    <label for="firstname">Age: </label>
    <input name="num" type="text" id="username" size="1">
    <input type="submit" value="Login" onclick="return validateForm()">

function validateForm()
{

    var z = document.forms["myForm"]["num"].value;
    if(!z.match(/^\d+/))
        {
        alert("Please only enter numeric characters only for your Age! (Allowed input:0-9)")
        }
}

Answer 1

function ValidateNumberOnly()
{
if ((event.keyCode < 48 || event.keyCode > 57)) 
{
   event.returnValue = false;
}
}

this function will allow only numbers in the textfield.

Answer 2

No need for the long code for number input restriction just try this code.

It also accepts valid int & float both values.

Javascript Approach

onload =function(){ 
  var ele = document.querySelectorAll('.number-only')[0];
  ele.onkeypress = function(e) {
     if(isNaN(this.value+""+String.fromCharCode(e.charCode)))
        return false;
  }
  ele.onpaste = function(e){
     e.preventDefault();
  }
}

<p> Input box that accepts only valid int and float values.</p>
<input class="number-only" type=text />

jQuery Approach

$(function(){

  $('.number-only').keypress(function(e) {
	if(isNaN(this.value+""+String.fromCharCode(e.charCode))) return false;
  })
  .on("cut copy paste",function(e){
	e.preventDefault();
  });

});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p> Input box that accepts only valid int and float values.</p>
<input class="number-only" type=text />

The above answers are for most common use case - validating input as a number.

But to allow few special cases like negative numbers & showing the invalid keystrokes to user before removing it, so below is the code snippet for such special use cases.

$(function(){
      
  $('.number-only').keyup(function(e) {
        if(this.value!='-')
          while(isNaN(this.value))
            this.value = this.value.split('').reverse().join('').replace(/[\D]/i,'')
                                   .split('').reverse().join('');
    })
    .on("cut copy paste",function(e){
    	e.preventDefault();
    });

});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p> Input box that accepts only valid int and float values.</p>
<input class="number-only" type=text />

Answer 3

// I use this jquery it works perfect, just add class nosonly to any textbox that should be numbers only:

$(document).ready(function () {
       $(".nosonly").keydown(function (event) {
           // Allow only backspace and delete
           if (event.keyCode == 46 || event.keyCode == 8) {
               // let it happen, don't do anything
           }
           else {
               // Ensure that it is a number and stop the keypress
               if (event.keyCode < 48 || event.keyCode > 57) {
              alert("Only Numbers Allowed"),event.preventDefault();
               }
           }
       });
   });

Answer 4

This one worked for me :

function validateForm(){

  var z = document.forms["myForm"]["num"].value;

  if(!/^[0-9]+$/.test(z)){
    alert("Please only enter numeric characters only for your Age! (Allowed input:0-9)")
  }

}

Answer 5

Regular expressions are great, but why not just make sure it's a number before trying to do something with it?

function addemup() {
var n1 = document.getElementById("num1");
var n2 = document.getElementById("num2");
sum = Number(n1.value) + Number(n2.value);
    if(Number(sum)) {
        alert(sum);
        } else {
            alert("Numbers only, please!");
        };
    };

Answer 6

here is how to validate the input to only accept numbers this will accept numbers like 123123123.41212313

<input type="text" 
onkeypress="if ( isNaN(this.value + String.fromCharCode(event.keyCode) )) return false;"
/>

and this will not accept entering the dot (.), so it will only accept integers

<input type="text" 
onkeypress="if ( isNaN( String.fromCharCode(event.keyCode) )) return false;"
/>

this way you will not permit the user to input anything but numbers