I have two unrelated classes and a function that interacts with the constructor.name I don't want to use the any type. Is there a way I can write the following in a typescript way? I want someClass to represent any class but I'm not exactly sure how to write that.
class MyClass {
//
}
class MyOtherClass {
//
}
const getClassName = (someClass, name = someClass.constructor.name) => {
console.log(someClass)
console.log(someClass.constructor.name)
}
getClassName(MyClass)
You can define the type for a class constructor, like this:
type ClassConstructor<T> = {
new (...args: any[]): T;
};
const getClassName = (someClass: ClassConstructor<any>) => {
console.log(someClass.name)
}
getClassName(MyClass)
getClassName(MyOtherClass)
// this is a complie error: not a constructor
getClassName(() => 1)
// this is a complie error: instance - not a class
getClassName(new MyClass())
But beware, that the class-name may be different in production: i.e. when you use webpack to minify/uglify your code
From the lib.es5.d.ts (the file with Record / Partial / etc definitions) you can see builtin definition of
/**
* Obtain the return type of a constructor function type
*/
type InstanceType<T extends abstract new (...args: any) => any> = T extends abstract new (...args: any) => infer R ? R : any;
So, the constructor is defined as
type Constructor<T> = abstract new (...args: any) => T;
And your function is
const getClassName = (someClass: Constructor<any>, name = someClass.constructor.name) => {
console.log(someClass)
console.log(someClass.constructor.name)
}
or
const getClassName = (someClass: abstract new (...args: any) => any, name = someClass.constructor.name) => {
console.log(someClass)
console.log(someClass.constructor.name)
}
If you want to use the class name and keep your class itself on type level, you can use Branded (oko Opaque) types:
type Constructor<T> = abstract new (...args: any) => T;
// I tend to name non-object subtipes camelCase
type className<T> = string & {__classNameOf: T}
// or
declare const classNameOfSymbol: unique symbol
type className2<T> = string & {[classNameOfSymbol]: T}
function getClassName<T> (someClass: Constructor<T>, name = someClass.constructor.name): className<T> {
return name as className<T>
}
new (...args: any[]) => any