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Check If A Character Is A Letter In JavaScript - LearnShareIT

Check If A Character Is A Letter In JavaScript

Check If A Character Is A Letter In JavaScript

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!

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