In JavaScript language, we have several ways to check if a character is a letter in JavaScript. Below we will show you how to do it with 2 methods: use the regular expression method and a combination of toLowerCase() and toUppercase() method.
How to check if a character is a letter in JavaScript
Using regular expression
In this method, to check if a character is a letter, you should learn about regular expressions first.
You can refer to the structure below:
function isCharacterALetter(char) { if (char.length !== 1) { return false; } return /[a-zA-Z]/.test(char); }
Parameter:
- char: is any character, except special characters.
The first thing we do is we will check if char
is a string by checking its number of characters via the length()
method. The expression /[a-zA-Z]/
means to match all strings that start with a letter. If char matches a value in the regex pattern and is treated as a letter of the alphabet, the test()
method will return a true result. A false value will be returned if the char value does not match the regular expression.
Example:
function isCharacterALetter(char) { if (char.length !== 1) { return false; } return /[a-zA-Z]/.test(char); } console.log(isCharacterALetter("a")); console.log(isCharacterALetter("b")); console.log(isCharacterALetter("6")); console.log(isCharacterALetter("32")); console.log(isCharacterALetter("Abc"));
Output
true
true
false
false
false
Using toLowerCase() and toUppercase() methods
The toLowerCase()
method converts a string to a regular string. And the toUppercase()
method converts a string to uppercase.
Syntax:
str.toLowerCase();
str.toUpperCase();
Parameter: NONE.
Similar to the above solution, we will check if the char
is a string using the length()
method.
We use compare char.toLowerCase()! = char.toUpperCase()
to check if the char
in lowercase and uppercase are different. Because the letter can be lowercase or uppercase and the remaining characters are not case-sensitive uppercase and lowercase letters. This means that non-characters in lowercase and uppercase are identical.
Example:
function isLetter(char) { if (char.length !== 1) { return false; } return char.toLowerCase() != char.toUpperCase(); } console.log(isLetter("e")); console.log(isLetter("A")); console.log(isLetter("6")); console.log(isLetter("123")); console.log(isLetter("Hello"));
Output
true
true
false
false
false
Summary
So, we have learned some methods to check if a character is a letter in JavaScript. It’s different. You need to know regular expressions or some string-handling functions. You should read carefully to better understand. Good luck for you!
Maybe you are interested:
- How To Replace Underscores With Spaces In A String Using JS
- Check if String contains only Digits in JavaScript
- Check if String contains Special Characters in JavaScript

My name is Tom Joseph, and I work as a software engineer. I enjoy programming and passing on my experience. C, C++, JAVA, and Python are my strong programming languages that I can share with everyone. In addition, I have also developed projects using Javascript, html, css.
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