Implementing function overloading

Question

Since javascript does not support function overloading typescript does not support it. However this is a valid interface declaration:

// function overloading only in the interface 
interface IFoo{
    test(x:string);
    test(x:number);
}

var x:IFoo;
x.test(1);
x.test("asdf");

But how can I implement this interface. Typescript does not allow this code:

// function overloading only in the interface 
interface IFoo{
    test(x:string);
    test(x:number);
}

class foo implements IFoo{
    test(x:string){

    }
    test(x:number){

    }
}

Try it

The reason for adding the functionality to interfaces is quite clear. This is what allows us to describe (via interfaces) how jquery works. But how I would write something like jquery in typescript is what I am trying to understand. — basarat
– basarat, Commented Mar 13, 2013 at 3:52
Does this answer your question? TypeScript function overloading — Cuminato
– Cuminato, Commented Sep 4, 2023 at 14:06

GJK · Accepted Answer · 2013-03-13 03:54:34Z

5

Function overloading in Typescript is done like this:

class foo implements IFoo {
    test(x: string);
    test(x: number);
    test(x: any) {
        if (typeof x === "string") {
            //string code
        } else {
            //number code
        }
    }
}

answered Mar 13, 2013 at 3:54

GJK

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