How to Check if Input Contains Only Letters in Javascript
In this tutorial, you will learn how to check if input contains only letters in javascript. In HTML, input element is suitable for a single line text content and textarea element is suitable for multiline text content. Letters play an important role in the formation of a word and with the help of those words, we can create meaningful sentences. From a developer perspective, it can be a bit tricky to find if an input contains only letters.
There are numerous ways to check if an input contains only letters. But for the sake of simplicity, we will use the regular expression and ternary operator (?
) to accomplish our goal. The test()
method of RegExp object is used to perform a pattern search in a string and returns a Boolean value.
In the following example, we have one textbox where we will enter some random text. Upon click of a button, we will check if the input contains only letters and display the result on the screen. Please have a look over the code example and the steps given below.
HTML & CSS
- We have 4 elements in the HTML file (
div
,input
,button
, andh1
). Thediv
element is just a wrapper for the rest of the elements. - The
innerText
for thebutton
element is“Check”
and for theh1
element, it is“Result”
. - We have done some basic styling using CSS and added the link to our
style.css
stylesheet inside thehead
element. - We have also included our javascript file
script.js
with ascript
tag at the bottom.
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <link rel="stylesheet" href="style.css"> <title>Document</title> </head> <body> <div class="container"> <input type="text" /> <button>Check</button> <h1>Result</h1> </div> <script src="script.js"></script> </body> </html>
.container { text-align: center; } button { margin-top: 10px; padding: 10px 20px; } input { display: block; padding: 5px 10px; margin: auto; }
Javascript
- We have selected the
button
element,input
element, andh1
element using thedocument.querySelector()
method and stored them inbtnCheck
,inputEl
, andoutput
variables respectively. - We have attached a
click
event listener to thebutton
element. - We have the
regExp
variable which holds a regular expression/^[a-z]+$/i
as its value to match only letters. - In the event handler function, we are getting value from the input element and storing it in the
value
variable. - We are calling the
test()
method ofregExp
and passingvalue
as a parameter. It will return a Boolean value which we are storing in thefound
variable. - We are using the ternary operator (
?
) and checking whetherfound
is true or false. If it is true, that means the input contains only letters. - Depending upon the result of the check, we will assign
“Yes”
or“No”
to theresult
variable. - We are displaying the
result
in theh1
element using theinnerText
property.
let btnCheck = document.querySelector("button"); let inputEl = document.querySelector("input"); let output = document.querySelector("h1"); let regExp = /^[a-z]+$/i; btnCheck.addEventListener("click", () => { let value = inputEl.value; let found = regExp.test(value) let result = found ? "Yes" : "No"; output.innerText = result; });