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.
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) {
}