samnoh / ts-express

TypeScript + Express.js

TIL

Mapped Types

type Roles = 'isUser' | 'isAdmin';
const userHandler = (role: { [K in Roles]: boolean }): void => { ... };

userHandler({'isUser': false});
userHandler({'newKey': true}); // error!

Express

• Type Definition

npm install --save-dev @types/express

• Usage

import express, { Express, Request, Response, NextFunction } from 'express';
const app: Express = express();
app.get('/', (req: Request, res: Response, next: NextFunction) => { ... });

d.ts

• Triple-Slash Directives
  • import type definition in TypeScript

/// <reference types="modulename" />

• namespace
  • internal modules
  • interfaces can be merged (override)

import modulename = require('modulename');

declare namespace "modulename" {
    export interface aaa { }
    export class bbb { }
}

reflect-metadata

• npm

• Install

npm install --save-dev reflect-metadata

• tsconfig.json

"experimentalDecorators": true,
"emitDecoratorMetadata": true

• Reflect.defineMetadata(metadataKey, metadataValue, C.prototype, "method")
• Reflect.getMetadata(metadataKey, obj, "method")

import 'reflect-metadata';

@classDeco
class User {
    name: string = 'smith';

    @describeUser('happy', 'kind', 'verbose'); // -> 'happy kind verbose'
    printName(): void {
        console.log(this.name);
    }
}

function classDeco(target: any) {
    for (let key in target.prototype) {
        const description: string[] = Reflect.getMetadata('desc', target.prototype, key) || [];
        console.log(...description);
    }
}

function describeUser(...keys: string[]) {
    return function (target: any, key: string, desc: PropertyDescriptor) {
        Reflect.defineMetadata('desc', keys, target, key);
    }
}

Unix Copy

cp -r [folder] [dest folder]

module-alias

• Create aliases of directories and register custom module paths

• npm

• Install

npm install --save module-alias

• import

import 'module-alias/register'; // at the very main file of your app, before any code

• tsconfig.json

"baseUrl": "./src",
"path": {
    "@util": ["util/index"],
    "@lib/*": ["lib/*"]
}

• package.json

"_moduleAliases": {
    "@util": "build/util/index.js",
    "@lib": "build/lib"
}

• Usage

import { foo } from '@util';
import { getUsers } from '@lib/users';