♻️ TypeScript function overloading

import ow from "ow"; function myMethod(a: string): string; function myMethod(a: number): number; function myMethod(a: number, b: string): [number, string]; function myMethod( a: string | number, b?: string ): string | number | [number, string] { if (ow.isValid(a, ow.string) && ow.isValid(b, ow.undefined)) { console.log("function myMethod(a: string): string"); return a; } if (ow.isValid(a, ow.number) && ow.isValid(b, ow.undefined)) { console.log("function myMethod(a: number): number"); return a; } if (ow.isValid(a, ow.number) && ow.isValid(b, ow.string)) { console.log("function myMethod(a: number, b: string): [number, string]"); return [a as number, b]; } } console.log(myMethod(123)); // function myMethod(a: number): number // 123 console.log(myMethod("Andrew")); // function myMethod(a: string): string // Andrew console.log(myMethod(123, "Andrew")); // function myMethod(a: number, b: string): [number, string] // [123, "Andrew"] 

import ow from "ow"; class MyClass { myMethod(a: string): string; myMethod(a: number): number; myMethod(a: number, b: string): [number, string]; myMethod( a: string | number, b?: string ): string | number | [number, string] { if (ow.isValid(a, ow.string) && ow.isValid(b, ow.undefined)) { console.log("function myMethod(a: string): string"); return a; } if (ow.isValid(a, ow.number) && ow.isValid(b, ow.undefined)) { console.log("function myMethod(a: number): number"); return a; } if (ow.isValid(a, ow.number) && ow.isValid(b, ow.string)) { console.log("function myMethod(a: number, b: string): [number, string]"); return [a as number, b]; } } } const myClass = new MyClass() console.log(myClass.myMethod(123)); // function myMethod(a: number): number // 123 console.log(myClass.myMethod("Andrew")); // function myMethod(a: string): string // Andrew console.log(myClass.myMethod(123, "Andrew")); // function myMethod(a: number, b: string): [number, string] // [123, "Andrew"]