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Javascript how to validate input text field for Numbers, Decimal, Uppercase, Lowercase and String data

The following Javascript uses the test() method tests for a match in a string. This method returns true if it finds a match, otherwise it returns false. This is very helpful when testing for Username, password, dollar amounts, etc. in HTML forms.
  • Syntax: RegExpObject.test(string)

JavaScript: Test input fields for Valid Data

This JavaScript validates character input the user can enter into an input or textarea. This is useful in aiding the user enter the correct information such as a number or username.


Check for Numbers:



Check for upto 2 Decimal:



Check for Uppercase String:



Check for Lowercase String:



Check for String:




Complete Source code for the above example

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Check input fields for Valid Data</title>
<script type="text/javascript">

 var numbersOnly = /^\d+$/;
 var decimalOnly = /^\s*-?[1-9]\d*(\.\d{1,2})?\s*$/;
 var uppercaseOnly = /^[A-Z]+$/;
 var lowercaseOnly = /^[a-z]+$/;
 var stringOnly = /^[A-Za-z0-9]+$/;

 function testInputData(myfield, restrictionType) {

  var myData = document.getElementById(myfield).value;
  if(myData!==''){
   if(restrictionType.test(myData)){
    alert('It is GOOD!');
   }else{
    alert('Your data input is invalid!');
   }
  }else{
   alert('Please enter data!');
  }
  return;
    
 }
 </script>
</head>

<body>
 <h1>JavaScript: Test input fields for Valid Data</h1>
 <p>This JavaScript validates character input the user can enter
  into an input or textarea. This is useful in aiding the user enter the
  correct information such as a number or username.</p>
 <form name="as400samplecode" action="" method="get">

  <table>

   <tr>
    <td>Check for Numbers:</td>
    <td><input type="text" id="input1" maxlength="30" size="30" />
    </td>
    <td><input type="button" value="Test"
     onclick="Javascript:testInputData('input1',numbersOnly)" /></td>
   </tr>
   <tr>
    <td>Check for upto 2 Decimal:</td>
    <td><input type="text" id="input2" maxlength="30" size="30" />
    </td>
    <td><input type="button" value="Test"
     onclick="Javascript:testInputData('input2',decimalOnly)" /></td>
   </tr>
   <tr>
    <td>Check for Uppercase String:</td>
    <td><input type="text" id="input3" maxlength="30" size="30" />
    </td>
    <td><input type="button" value="Test"
     onclick="Javascript:testInputData('input3',uppercaseOnly)" /></td>
   </tr>
   <tr>
    <td>Check for Lowercase String:</td>
    <td><input type="text" id="input4" maxlength="30" size="30" />
    </td>
    <td><input type="button" value="Test"
     onclick="Javascript:testInputData('input4',lowercaseOnly)" /></td>
   </tr>
   <tr>
    <td>Check for String:</td>
    <td><input type="text" id="input5" maxlength="30" size="30" />
    </td>
    <td><input type="button" value="Test"
     onclick="Javascript:testInputData('input5',stringOnly)" /></td>
   </tr>

  </table>

 </form>
</body>
</html>