Typescript !
Middleware Pattern, Typescript Implementation from scratch.
To apply in:
- Front or
- Back or
- Automation Tool or
- Command Line Tool
- My I have to use Command Pattern and Interpreter Pattern Mixed with Middleware Pattern.
Seems:
Like the old Filters in java web
But widely spread over platforms
Like the old Template in C++ .. ..
Reference:
// app.ts
import { pipeline } from './middleware';
interface Context {
[key: string]: any; // Yes, I Love semicolons.!!
};
const engine = pipeline<Context>( async (ctx, next) => {
ctx.first = "First things First!!";
next();
} );
engine.use( async (ctx, next) => {
ctx.second = "I am the developer:";
next();
} );
engine.use( async (ctx, next) => {
ctx.third = "https://github.com/maximilianou";
next();
} );
console.log('Running.. TypeScript app');
(async () => {
const context: Context = {};
await engine.execute(context);
console.log(context);
})();- middleware.js
// middleware.ts
export type Next = () => Promise<any> | any;
export type Middleware<T> = (
context: T,
next: Next
) => Promise<void>;
export type Pipe<T> = {
use: (...middlewares: Middleware<T>[]) => void;
execute: (context: T) => Promise<void | T>
};
export function pipeline<T>(...middlewares: Middleware<T>[])
: Pipe<T> {
const stack: Middleware<T>[] = middlewares;
const use: Pipe<T>["use"] = (...middlewares) => {
stack.push(...middlewares);
}
const execute: Pipe<T>["execute"] = async (context) => {
let prevIndex = -1;
const handler = async (index: number, context: T)
: Promise<void | T> => {
if(index === prevIndex){
throw new Error("next() already called");
}
if(index === stack.length ){
return context;
}
prevIndex = index;
const middleware = stack[index];
if(middleware){
await middleware( context, () => handler( index+1, context ) );
}
};
const response = await handler(0, context);
if (response){
return response;
}
};
return { use, execute };
}- Makefile
api:
mkdir api && cd api && npm -y init
cd api && npm i express-openapi-validator
cd api && npm i @types/node typescript
cd api && npm install ts-node -D
cd api && ./node_modules/.bin/tsc --init --rootDir src --outDir ./build --esModuleInterop --lib esnext --module esnext --noImplicitAny true
cd api && mkdir src
cd api && echo "console.log('Running.. TypeScript app')" > src/app.ts
cd api && ./node_modules/.bin/tsc
cd api && node ./build/app.js
- package.json
{
"name": "api",
"version": "1.0.0",
"description": "",
"main": "app.ts",
"scripts": {
"build":"./node_modules/.bin/tsc ",
"start":"node ./build/app.js",
"dev": "./node_modules/.bin/ts-node ./src/app.ts",
"test": "echo \"Error: no test specified\" && exit 1"
},
"keywords": [],
"author": "",
"license": "ISC",
"dependencies": {
"@types/node": "^14.14.22",
"express-openapi-validator": "^4.10.9",
"typescript": "^4.1.3"
},
"devDependencies": {
"ts-node": "^9.1.1"
}
}- tsconfig.json
{
"compilerOptions": {
/* Visit https://aka.ms/tsconfig.json to read more about this file */
/* Basic Options */
// "incremental": true, /* Enable incremental compilation */
"target": "es5", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
"module": "commonjs", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
"lib": ["esnext"], /* Specify library files to be included in the compilation. */
// "allowJs": true, /* Allow javascript files to be compiled. */
// "checkJs": true, /* Report errors in .js files. */
// "jsx": "preserve", /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
// "declaration": true, /* Generates corresponding '.d.ts' file. */
// "declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
// "sourceMap": true, /* Generates corresponding '.map' file. */
// "outFile": "./", /* Concatenate and emit output to single file. */
"outDir": "./build", /* Redirect output structure to the directory. */
"rootDir": "src", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
// "composite": true, /* Enable project compilation */
// "tsBuildInfoFile": "./", /* Specify file to store incremental compilation information */
// "removeComments": true, /* Do not emit comments to output. */
// "noEmit": true, /* Do not emit outputs. */
// "importHelpers": true, /* Import emit helpers from 'tslib'. */
// "downlevelIteration": true, /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
// "isolatedModules": true, /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
/* Strict Type-Checking Options */
"strict": true, /* Enable all strict type-checking options. */
"noImplicitAny": true, /* Raise error on expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* Enable strict null checks. */
// "strictFunctionTypes": true, /* Enable strict checking of function types. */
// "strictBindCallApply": true, /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
// "strictPropertyInitialization": true, /* Enable strict checking of property initialization in classes. */
// "noImplicitThis": true, /* Raise error on 'this' expressions with an implied 'any' type. */
// "alwaysStrict": true, /* Parse in strict mode and emit "use strict" for each source file. */
/* Additional Checks */
// "noUnusedLocals": true, /* Report errors on unused locals. */
// "noUnusedParameters": true, /* Report errors on unused parameters. */
// "noImplicitReturns": true, /* Report error when not all code paths in function return a value. */
// "noFallthroughCasesInSwitch": true, /* Report errors for fallthrough cases in switch statement. */
// "noUncheckedIndexedAccess": true, /* Include 'undefined' in index signature results */
/* Module Resolution Options */
"moduleResolution": "node", /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
"baseUrl": "./", /* Base directory to resolve non-absolute module names. */
"paths": {
"@exmpl/*": ["src/*","build/*"]
}, /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
// "rootDirs": [], /* List of root folders whose combined content represents the structure of the project at runtime. */
// "typeRoots": [], /* List of folders to include type definitions from. */
// "types": [], /* Type declaration files to be included in compilation. */
// "allowSyntheticDefaultImports": true, /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
"esModuleInterop": true, /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
// "preserveSymlinks": true, /* Do not resolve the real path of symlinks. */
// "allowUmdGlobalAccess": true, /* Allow accessing UMD globals from modules. */
/* Source Map Options */
// "sourceRoot": "", /* Specify the location where debugger should locate TypeScript files instead of source locations. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSourceMap": true, /* Emit a single file with source maps instead of having a separate file. */
// "inlineSources": true, /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
/* Experimental Options */
// "experimentalDecorators": true, /* Enables experimental support for ES7 decorators. */
// "emitDecoratorMetadata": true, /* Enables experimental support for emitting type metadata for decorators. */
/* Advanced Options */
"skipLibCheck": true, /* Skip type checking of declaration files. */
"forceConsistentCasingInFileNames": true /* Disallow inconsistently-cased references to the same file. */
}
}- Result
$ npm run dev
> api@1.0.0 dev /home/maximilianou/projects/weekly27/api
> ts-node ./src/app.ts
Running.. TypeScript app
{
first: 'First things First!!',
second: 'I am the developer:',
third: 'https://github.com/maximilianou'
}
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