Validate UUID without RegExp

Question

JavaScript Array.every() does not work the way I expected

I have been tasked with writing a basic check for GUID validity without using regex. So all I'm doing is checking if the non-dash characters in the guid string are hexa digits.

const isValidGUIDChar = (char) =>  !isNaN(+char) || "abcdef".includes(char.toLowerCase());

// let guid = "123";
// let guid = "abc"
let guid = "abc123";

let isGuidValid = guid.replaceAll('-', '').length === 32 && guid.split().every(isValidGUIDChar);

console.log(isGuidValid);  // returns true for either 'abc' or '123' but false for 'abc123'

The results, mention in comment above are counter-intuitive. The every() method seems to evaluate to:

"(every character must either be numeric), or (every character must be from among 'abcdef')",

whereas what I need, and what seems intuitive, would be for it to evaluate to:

"(every character) must (either be numeric from among 'abcdef')"

How can I accomplish the latter?

Answer 1

• Your .split() is missing "" (BTW, use [...guid] with Spread instead)
• Make sure you actually test with 32 char after! you replace all dashes
• Use it as a function isGuidValid(guid) - reusability, remember?

const isHEX = (ch) => "0123456789abcdef".includes(ch.toLowerCase());

const isGuidValid = (guid) => {
  guid = guid.replaceAll("-", ""); // Format it first!
  return guid.length === 32 && [...guid].every(isHEX);
};

console.log(isGuidValid("adec3dc3-7025-4905-b584-d9e64117f2fd"));  // true
console.log(isGuidValid("adec3dc3-7025-4905-b584-d9e64117f2fz"));  // false
console.log(isGuidValid("adec3dc3-7025-4905-b584-d9e64117f2f"));   // false

A more robust approach, taking in consideration the RFC4122 treating a GIUD/UUID as groups of 8-4-4-4-12 codepoint chars each would be:

const isHEX = h => !isNaN(parseInt(h, 16));
const RFC4122Len = [8, 4, 4, 4, 12];

const isGuidValid = (guid) => {

  // Must have 36 Chars per codepoint (32 + 4 dashes)
  const codePointLenght = [...guid].length;
  if (codePointLenght !== 36) return false;

  // Must have 5 groups
  const groups = guid.split("-");
  if (groups.length !== 5) return false;

  // RFC defines 5 groups of 8-4-4-4-12 codepoints chars each
  const lenMatch = groups.map(gr => [...gr].length).every((len, i) => len === RFC4122Len[i]);
  if (!lenMatch) return false;

  // Finally join groups (without the "-" separators and check for each char is HEX)
  return [...(groups.join(""))].every(isHEX);
};

console.log(isGuidValid("adec3dc3-7025-4905-b584-d9e64117f2fd")); // true
console.log(isGuidValid("adec3dc3-7025-4905-b584-d9e64117f2fz")); // false
console.log(isGuidValid("adec3dc3-7025-4905-b584-d9e64117f2f"));  // false

There's more to make it fully RFC4122 compliant but you got the general idea.