What is the InstanceType utility type?

InstanceType<T> extracts the instance type of a constructor function or class. It takes a class constructor type and returns the type of the instances that constructor creates. Implementation: type InstanceType<T extends abstract new (...args: any) => any> = T extends abstract new (...args: any) => infer R ? R : any. Usage: class User { name: string; constructor(name: string) { this.name = name; } } type UserInstance = InstanceType<typeof User>; — UserInstance is the same as the User type (the instance type). Most useful when working with class references passed as parameters or stored in variables: function createInstance<T extends new (...args: any) => any>(ctor: T): InstanceType<T> { return new ctor(); } — this factory function returns the correct instance type regardless of which class is passed. Related: ConstructorParameters<T> extracts the constructor's parameter types.