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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

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04