tsargs

tsargs

TypeScript utility types for function arguments

• Pick type of specific argument
• Prepend arguments
• Append arguments

Tested with static asserts

Should use typescript 2.8 and upper

Install & use

npm i tsargs

import { Arg2 } from 'tsargs';

function foo(a: number, b: string) {}

const secondArg: Arg2<typeof foo> = 'hello world!';

Pick argument

Use ArgN type to pick N argument (max 10 arg)

import { Arg2 } from 'tsargs';

function foo(a: number, b: string) {}

const secondArg: Arg2<typeof foo> = 'hello world!';

Prepend arguments

Useful for typed callbacks, rpc or event

Use PreNArgJ type to prepend N arguments to function with J arguments (max 10 arg)
or PreNArgN type to prepend N arguments to function with unknown arguments number

import { Pre1Arg2, Pre1ArgN } from 'tsargs';

function foo(a: number, b: string) {}
function boo(x: string, a: number, b: string) {}

const booFromFoo: Pre1Arg2<string, typeof foo> = boo;
const booFromFoo2: Pre1ArgN<string, typeof foo> = boo;

PreNArgN type may cause low ts performance

Append arguments

Useful for typed callbacks, rpc or event

Use PostNArgJ type to append N arguments to function with J arguments (max 10 arg)
or PostNArgN type to append N arguments to function with unknown arguments number

import { Post1Arg2, Post1ArgN } from 'tsargs';

function foo(a: number, b: string) {}
function boo(a: number, b: string, x: string) {}

const booFromFoo: Post1Arg2<string, typeof foo> = boo;
const booFromFoo2: Post1ArgN<string, typeof foo> = boo;

PostNArgN type may cause low ts performance

Pick range of arguments

Callbacks & arguments list

Use Args10 to pick 10 args of function

Use ArgsNoffOffset to pick N args with Offset offset (max 10 arg)

import { Args2off1 } from 'tsargs';

function foo(a: boolean, b: number, c: string) {}
const argsBC: Args2off1<typeof foo> = [ 123, 'Hello' ];

Roadmap

• Example of typed event emitter
• ✔ Pick range of arguments to array type
• Pick any number of arguments to array type
• Pick arguments to object
• Specific argument's type replace
• Remove arguments
• Replace return type (not yet possible with buggy ts 3.0.3 rest parameters)

Write issue on github if you have any trouble with arguments in typescript