How to Check if String Contains Only Specific Characters in Javascript
In this tutorial, you will learn how to check if string contains only specific characters in javascript. A string consists of multiple characters and these characters can be letters, numbers, or special characters. For a beginner, it can be a bit tricky to find if a string contains only specific characters.
There are numerous ways to check if a string contains only specific characters. We are going to use one of the easiest solutions which involve the usage of the match()
method and ternary (?
) operator.
The match()
methods matches a string against a regular expression. If the match is found, it returns an array of matches, otherwise returns null. The ternary operator is also known as the conditional operator which acts similar to the if-else statement.
In the following example, we have one global variable and upon click of a button, we will check if the string contains only specific characters and display the result on the screen. Please have a look over the code example and the steps given below.
HTML & CSS
- We have 3 elements in the HTML file (
div
,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"> <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; }
Javascript
- We have selected the
button
element andh1
element using thedocument.querySelector()
method and stored them inbtnCheck
andoutput
variables respectively. - We have attached a
click
event listener to thebutton
element. - We have a global variable
myVar
which holds a string as its value. - In the event handler function, we have
pattern
variable which holds a regex pattern. - We are using
match()
method and ternary (?
) operator to verify whethermyVar
matches a regex pattern or not. The pattern will match only charactersh
,e
,l
ando
. The match will fail if the string contains any other characters apart from those specific characters. - 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 output = document.querySelector("h1"); let myVar = "hello"; btnCheck.addEventListener("click", () => { let pattern = /^[helo]*$/; let result = myVar.match(pattern) ? "Yes" : "No"; output.innerText = result; });