JavaScript: HTML Form validation - checking for all numbers

Last update on August 19 2022 21:50:37 (UTC/GMT +8 hours)

Checking for all numbers

Sometimes situations arise (input a phone number, zip code or credit card number) when the user should fill a single or more than one fields with numbers (0-9) in an HTML form. You can write JavaScript scripts to check the following validations.

To check for all numbers in a field.
An integer with an optional leading plus(+) or minus(-) sign.

Following code blocks contain actual codes for the said validations. We have kept the CSS code part common for all the validations.

CSS Code

li {list-style-type: none;
font-size: 16pt;
}
.mail {
margin: auto;
padding-top: 10px;
padding-bottom: 10px;
width: 400px;
background : #D8F1F8;
border: 1px soild silver;
}
.mail h2 {
margin-left: 38px;
}
input {
font-size: 20pt;
}
input:focus, textarea:focus{
background-color: lightyellow;
}
input submit {
font-size: 12pt;
}
.rq {
color: #FF0000;
font-size: 10pt;
}

To check for all numbers in a field

To get a string contains only numbers (0-9) we use a regular expression (/^[0-9]+$/) which allows only numbers. Next, the match() method of the string object is used to match the said regular expression against the input value. Here is the complete web document.

HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>JavaScript form validation - checking all numbers</title>
<link rel='stylesheet' href='form-style.css' type='text/css' />
</head>
<body onload='document.form1.text1.focus()'>
<div class="mail">
<h2>Input your registration number and submit</h2>
<form name="form1" action="#">
<ul>
<li><input type='text' name='text1'/></li>
<li class="rq">*Enter numbers only.</li>
<li>&nbsp;</li>
<li><input type="submit" name="submit" value="Submit" onclick="allnumeric(document.form1.text1)" /></li>
<li>&nbsp;</li>
</ul>
</form>
</div>
<script src="all-numbers.js"></script>
</body>
</html>

JavaScript Code

function allnumeric(inputtxt)
   {
      var numbers = /^[0-9]+$/;
      if(inputtxt.value.match(numbers))
      {
      alert('Your Registration number has accepted....');
      document.form1.text1.focus();
      return true;
      }
      else
      {
      alert('Please input numeric characters only');
      document.form1.text1.focus();
      return false;
      }
   }

Flowchart:

View the example in the browser

An integer with an optional leading plus(+) or minus(-) sign

To get a string contains only numbers (0-9) with a optional + or - sign (e.g. +1223, -4567, 1223, 4567) we use the regular expression (/^[-+]?[0-9]+$/). Next, the match() method of the string object is used to match the said regular expression against the input value. Here is the complete web document.

HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>JavaScript form validation - An integer with an optional leading plus(+) or minus(-) sign</title>
<link rel='stylesheet' href='form-style.css' type='text/css' />
</head>
<body onload='document.form1.text1.focus()'>
<div class="mail">
<h2>Input your registration number and submit</h2>
<form name="form1" action="#">
<ul>
<li><input type='text' name='text1'/></li>
<li class="rq">*Enter numbers only.</li>
<li>&nbsp;</li>
<li><input type="submit" name="submit" value="Submit" onclick="allnumericplusminus(document.form1.text1)" /></li>
<li>&nbsp;</li>
</ul>
</form>
</div>
<script src="all-numbers-with-plus-minus.js"></script>
</body>
</html>

JavaScript Code

function allnumericplusminus(inputtxt)
   {
      var numbers = /^[-+]?[0-9]+$/;
      if(inputtxt.value.match(numbers))
      {
      alert('Correct...Try another');
      document.form1.text1.focus();
      return true;
      }
      else
      {
      alert('Please input correct format');
      document.form1.text1.focus();
      return false;
      }
   }

Flowchart:

View the example in the browser

Download the validation code from here.

Other JavaScript Validation :

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