Typeof arguments object in TypeScript

Question

I basically have this:

function foo(){

 // literally pass the arguments object into the pragmatik.parse method
 // the purpose of pragmatik.parse is to handle more complex variadic functions

 const [a,b,c,d,e] = pragmatik.parse(arguments);

 // now we have the correct arguments in the expected location, using array destructuring


}

so we have the pragmatik.parse method:

function parse(args){

   // return parsed arguments

}

now I want to use TypeScript to define types, all I know is that arguments is an Object:

function parse(args: Object){


}

so my question is: does TypeScript give a definition or type for an arguments object in JS? Sorry this is a bit meta, but please bear with me, what I am asking about is sane.

Alexander Mills · Accepted Answer · 2017-11-12 07:41:08Z

1

My Webstorm IDE suggests that this might be IArguments, which is provided by: lib/es6/d.ts, which is somewhere out there. Maybe someone can verify this is correct, but I am fairly certain.

So the answer would be:

function parse(args: IArguments){


}

and the full signature would be:

function parse(args: IArguments) : Array<any> {


}

since the parse method returns a generic array

edited Nov 12, 2017 at 7:41

answered Mar 3, 2017 at 6:53

Alexander Mills

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Morglod · Accepted Answer · 2018-09-03 12:53:33Z

1

You can pick exact type of arguments with tsargs package from npm

Eg:

import { ArgsN } from 'tsargs';

function foo(a: boolean, b: number, c: string) {}
const argsABC: ArgsN<typeof foo> = [ true, 123, 'Hello' ];

In your case:

import { ArgsN } from 'tsargs';

function parse<T extends (...args: any[]) => any>(args: IArguments): ArgsN<T> {
    // return parsed arguments
}

// ...

const args = parse<typeof foo>(arguments);
// args -> [ boolean, number, string ];

answered Sep 3, 2018 at 12:53

Morglod

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