Using JavaScript to Check if String Contains Letters

There are many ways we can use JavaScript to check if a string contains a letter. We will go over two simple methods below to do this.

The first uses the JavaScript test() method and a regex expression.

/[a-zA-Z]/.test(someString);

The regex expression /[a-zA-Z]/ will check for any letter, lowercase or uppercase. The test() method will check the string you pass as a parameter to see if a letter is contained in the string due to the regex expression. If it does find it, it returns true. Otherwise, it returns false.

We can wrap this code in a function to make it easy to reuse.

function stringContainsLetter(str){
  return /[a-zA-Z]/.test(str);
};

Now let’s test this function with a couple of examples:

function stringContainsLetter(str){
  return /[a-zA-Z]/.test(str);
};

var string1 = "This is a string with letters.";
var string2 = "    ";
var string3 = "10000c23339";
var string4 = "123456";
var string5 = 12;

console.log(stringContainsLetter(string1));
console.log(stringContainsLetter(string2));
console.log(stringContainsLetter(string3));
console.log(stringContainsLetter(string4));
console.log(stringContainsLetter(string5));

#Output
true
false
true
false
false

Using JavaScript match() Method to Check if String Contains Letter

We can also use the match() method to check if a string contains a letter along with a regex expression as we did with the test method.

someString.match(/[a-zA-Z]/);

The match() method will search the string, someString, for whatever you pass in as the parameter, which in this case is our regex expression for a letter. The match() method will return an array with all of the matches, otherwise if a match is not found, it will return null.

Let’s put this code in a function as we did with the test() method.

function stringContainsLetter(str){
  if( str.match(/[a-zA-Z]/) != null ){
    return true;
  } else {
    return false;
  }
};

And finally, let’s test this function as we did with our first function.

Now let’s test this function with a couple of examples:

function stringContainsLetter(str){
  if( str.match(/[a-zA-Z]/) != null ){
    return true;
  } else {
    return false;
  }
};

var string1 = "This is a string with letters.";
var string2 = "    ";
var string3 = "10000c23339";
var string4 = "123456";

console.log(stringContainsLetter(string1));
console.log(stringContainsLetter(string2));
console.log(stringContainsLetter(string3));
console.log(stringContainsLetter(string4));

#Output
true
false
true
false

Hopefully this article has been useful for you to learn how to use JavaScript to check if a string contains letter.