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JavaScript: HTML Form validation - checking for all letters

Checking for all letters

Sometimes situations arise when a user should fill a single or more than one fields with alphabet characters (A-Z or a-z) in an HTML form. You can write a JavaScript form validation script to check whether the required field(s) in the HTML form contains only letters.

Javascript function to check for all letters in a field

function allLetter(inputtxt)
  {
   var letters = /^[A-Za-z]+$/;
   if(inputtxt.value.match(letters))
     {
      return true;
     }
   else
     {
     alert("message");
     return false;
     }
  }
  
  

To get a string contains only letters (both uppercase or lowercase) we use a regular expression (/^[A-Za-z]+$/) which allows only letters. Next the match() method of string object is used to match the said regular expression against the input value. Here is the complete web document.

Flowchart:

Flowchart: Javascript function to check for all letters in a field

HTML Code

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

JavaScript Code

function allLetter(inputtxt)
      { 
      var letters = /^[A-Za-z]+$/;
      if(inputtxt.value.match(letters))
      {
      alert('Your name have accepted : you can try another');
      return true;
      }
      else
      {
      alert('Please input alphabet characters only');
      return false;
      }
      }
	  

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 solid 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;
}

View the example in the browser

Practice the example online

See the Pen all-letters-field-1 by w3resource (@w3resource) on CodePen.


file_download Download the validation code from here.

Other JavaScript Validation :

Previous: JavaScript: HTML Form - checking for non empty field
Next: JavaScript: HTML Form validation - checking for all numbers



JavaScript: Tips of the Day

arrow function

const user = {
	email: "[email protected]",
	updateEmail: email => {
		this.email = email
	}
}

user.updateEmail("[email protected]")
console.log(user.email)

The updateEmail function is an arrow function, and is not bound to the user object. This means that the this keyword is not referring to the user object, but refers to the global scope in this case. The value of email within the user object does not get updated. When logging the value of user.email, the original value of [email protected] gets returned.

Ref: https://bit.ly/2IUFeTa