JavaScript Tutorial

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Allow only Numbers in Textbox Javascript

Learn to validate user input and restrict it to a certain format or range. For example, you may want to allow only numbers in a textbox and prevent the user from entering any other characters. In this tutorial, we will show you how to achieve this using JavaScript, specifically the onkeypress event. Additionally, we will demonstrate how to limit the input field to allow only numbers from 1 to 100 and display an error message if the user enters an invalid number

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Example 1 : Accept only Numbers in input field Javascript onkeypress

In this example, we use the onkeypress event to restrict input in a textbox to only numeric values. It checks if the character code of the pressed key (event.charCode) is between 48 and 57, which corresponds to the ASCII codes for digits 0 to 9

keypress only numbers Javascript

<input type="text" onkeypress="return event.charCode >= 48 && event.charCode <= 57">

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Example 2 : How to Make Input Accept only Numbers in Javascript?

In this second example of this tutorial, we use the isNaN function to check if the input value is a number or not. The isNaN function returns true if the value is not a number, and false otherwise. If the input value is a number, we allow it to be used in our program. Otherwise, we use an empty string instead of the invalid input.

Javascript Input fields allow only number Example

<script>
 var numericInput = document.getElementById('numericInput');
 numericInput.addEventListener('input', function(event) {
  var inputValue = event.target.value;
  var numericValue = parseInt(inputValue);
  if (isNaN(numericValue)) {
   event.target.value = '';
  } else {
   event.target.value = numericValue;
  }
 });
</script>

Run

Output of Javascript Textbox allow only number

Example 3 : Input Field Allow Only Numbers 1 to 100 in Javascript

In this third example of this tutorial, we will learn how to validate an input field using a JavaScript custom function and an if-else loop. The goal is to check whether the user has entered a valid number between 0 and 100, and display an appropriate message accordingly

 <script>
  function checkNumber() {
   var numberInput = document.getElementById('numberInput').value;
   var number = parseInt(numberInput);
   var message;
   if (isNaN(number)) {
    message = 'Please enter a valid number.';
   } else if (number < 1 || number > 100) {
    message = 'Please enter a number between 1 and 100.';
   } else {
    message = 'You entered a valid number between 1 and 100: ' + number;
   }
   alert(message);
  }
 </script>

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