To check if a string is a valid UUID (or a Universally unique identifier), we can use a special regex expression to check that in JavaScript.

TL;DR

// Regular expression to check if string is a valid UUID
const regexExp = /^[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12}$/gi;

// String with valid UUID separated by dash
const str = "a24a6ea4-ce75-4665-a070-57453082c256";

regexExp.test(str); // true

A valid UUID should have 5 sections separated by a dash (-) and in the first section it should have 8 characters, the second, third, and the fourth section should have 4 characters each, and the last section should have 12 characters with a total of 32characters.

All 5 sections should have characters either of the range from number 0 to 9, small alphabets a to f or capital alphabets A to F.

For an example, a valid UUID may look like this,

  a24a6ea4-ce75-4665-a070-57453082c256
#    8      4    4    4        12   characters = 32 total characters

So to check if a string is valid UUID we can use this regular expression,

// Regular expression to check if string is a valid UUID
const regexExp = /^[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12}$/gi;

This matches all the valid UUID since it checks for the above test cases.

Now let's write a string with valid UUID like this,

// Regular expression to check if string is a valid UUID
const regexExp = /^[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12}$/gi;

// String with valid UUID separated by dash
const str = "a24a6ea4-ce75-4665-a070-57453082c256";

Now to test the string, we can use the test() method available in the regular expression we defined. It can be done like this,

// Regular expression to check if string is a valid UUID
const regexExp = /^[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12}$/gi;

// String with valid UUID separated by dash
const str = "a24a6ea4-ce75-4665-a070-57453082c256";

regexExp.test(str); // true

• The test() method will accept a string type as an argument to test for a match.
• The method will return boolean true if there is a match using the regular expression and false if not.

See the above example live in JSBin.

If you want this as a utility function which you can reuse, here it is,

/* Check if string is valid UUID */
function checkIfValidUUID(str) {
  // Regular expression to check if string is a valid UUID
  const regexExp = /^[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12}$/gi;

  return regexExp.test(str);
}

// Use the function
checkIfValidUUID("a24a6ea4-ce75-4665-a070-57453082c256"); // true
checkIfValidUUID("a24a6ea4-ce75-4665-a070"); // false

That's all! 😃

Feel free to share if you found this useful 😃.

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