@oshx/type-helper NPM

@oshx/type-helper

This package includes the practical type helper for TypeScript users.

Installation

$ npm i -D @oshx/type-helper

Please add below in tsconfig.json file.

{
  "compilerOptions": {
    "typeRoots": [
      "node_modules/@oshx/type-helper"
    ]
  }
}

Ingredients

type ObjectKey
    // explicit constant object keys

type ObjectValue
    // explicit constant object values

interface PropsWithClassName
    // extendable interface with property 'className'

type AnyFunction
    // simply declared any function

Why it comes for?

The inspiration of this package is built for practical uses when often occurred. The first members of this package are below.

type ObjectKey, type ObjectValue

When you want to use the 'Enum' type in the TypeScript file, you could get a doubt that this built result is efficient.

enum EnumA {
  ENUM_1,
  ENUM_2,
}

function inputA(value: EnumA): EnumA {
    return 'ENUM_1' || 0 // EnumA Key or Value types are allowed!
}

As you might know, the 'Enum' of TypeScript could be caused below.

"use strict";

var EnumA;
(function (EnumA) {
  EnumA[EnumA["ENUM_1"] = 0] = "ENUM_1";
  EnumA[EnumA["ENUM_2"] = 1] = "ENUM_2";
})(EnumA || (EnumA = {}));

A key type and a value type are on the same level as the type.

You don't expect it, right? That's why it is here.

How to use

The case below is pretended in your TypeScript project.

export const ObjectA = {
  KEY_A: 'valueA',
  KEY_B: 'valueB',
} as const;

export type ObjectAKey = ObjectKey<typeof ObjectA>;
export type ObjectAValue = ObjectValue<typeof ObjectA>;

// TypeScript error would occur!
const shouldBeKeyOfA: ObjectAKey = 'KeyA';
const shouldBeValueOfA: ObjectAValue = 'ValueA';

// Passed!
const keyOfA: ObjectAKey = 'KEY_A';
const valueOfA: ObjectAValue = 'valueA';

You can distinguish the key and the value as types.

And below example is for the 'React' users with CSS-in-JS styling.

// expected a style extendable element!
import { ReactComponentElement, ReactElement } from 'react';

// assign a component to const
interface ConstantFunctionComponentProps extends PropsWithClassName, PropsWithChidren {
  title: string;
}

const ConstantFunctionComponent: ReactComponentElement<
  ConstantFunctionComponentProps
> = ({ title, children, className }) => {
  return (<div className={className}>{title} {children}</div>);
}

// declare a function component
interface FunctionStyleComponentProps {
  title: string;
}
function FunctionStyleComponent({
  title,
  children,
  className,
}: PropsWithClassName<
  PropsWithChildren<FunctionStyleComponentProps>
>): ReactElement {
  return <div className={className}>{title} {children}</div>;
}

It should be useful when you make a component with 'Styled Components' | 'Emotion Styled'

The package includes example JS-Doc.

This package will promise to you below.