GUID / UUID type in typescript

Question

I have this function:

function getProduct(id: string){    
    //return some product 
}

where id is actually GUID. Typescript doesn't have guid type. Is it possible create type GUID manually?

function getProduct(id: GUID){    
    //return some product 
}

so if instead 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx' will be some 'notGuidbutJustString' then I will see typescript compilation error.

Update: as David Sherret said: there is no way to ensure a string value based on regex or some other function at compile time but it is possible do all the checks in one place at run time.

Answer 1

You could create a wrapper around a string and pass that around:

class GUID {     private str: string;      constructor(str?: string) {         this.str = str || GUID.getNewGUIDString();     }      toString() {         return this.str;     }      private static getNewGUIDString() {         // your favourite guid generation function could go here         // ex: http://stackoverflow.com/a/8809472/188246         let d = new Date().getTime();         if (window.performance && typeof window.performance.now === "function") {             d += performance.now(); //use high-precision timer if available         }         return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {             let r = (d + Math.random() * 16) % 16 | 0;             d = Math.floor(d/16);             return (c=='x' ? r : (r & 0x3 | 0x8)).toString(16);         });     } }  function getProduct(id: GUID) {         alert(id); // alerts "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx" }  const guid = new GUID("xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx"); getProduct(guid); // ok getProduct("notGuidbutJustString"); // errors, good  const guid2 = new GUID(); console.log(guid2.toString()); // some guid string 

Update

Another way of doing this is to use a brand:

type Guid = string & { _guidBrand: undefined };  function makeGuid(text: string): Guid {   // todo: add some validation and normalization here   return text as Guid; }  const someValue = "someString"; const myGuid = makeGuid("ef3c1860-5ce6-47af-a13d-1ed72f65b641");  expectsGuid(someValue); // error, good expectsGuid(myGuid); // ok, good  function expectsGuid(guid: Guid) { } 

Answer 2

I think one should extend a bit on the answer by David Sherret.
Like this:

// export  class InvalidUuidError extends Error {     constructor(m?: string) {         super(m || "Error: invalid UUID !");          // Set the prototype explicitly.         Object.setPrototypeOf(this, InvalidUuidError.prototype);     }  }   // export  class UUID  {     protected m_str: string;      constructor(str?: string) {         this.m_str = str || UUID.newUuid().toString();          let reg:RegExp = new RegExp("[A-F0-9]{8}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{12}", "i")         if(!reg.test(this.m_str))             throw new InvalidUuidError();     }      toString() {         return this.m_str;     }      public static newUuid(version?:number) :UUID     {         version = version || 4;           // your favourite guid generation function could go here         // ex: http://stackoverflow.com/a/8809472/188246         let d = new Date().getTime();         if (window.performance && typeof window.performance.now === "function") {             d += performance.now(); //use high-precision timer if available         }         let uuid:string = ('xxxxxxxx-xxxx-' + version.toString().substr(0,1) + 'xxx-yxxx-xxxxxxxxxxxx').replace(/[xy]/g, (c) => {             let r = (d + Math.random() * 16) % 16 | 0;             d = Math.floor(d/16);             return (c=='x' ? r : (r & 0x3 | 0x8)).toString(16);         });          return new UUID(uuid);     } }   function getProduct(id: UUID) {         alert(id); // alerts "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx" }   const guid2 = new UUID(); console.log(guid2.toString()); // some guid string   const guid = new UUID("xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx"); getProduct(guid); // ok getProduct("notGuidbutJustString"); // errors, good