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https://github.com/darky/repl-ns

Namespace for REPL driven development for TypeScript/JavaScript
https://github.com/darky/repl-ns

clojure development driven javascript js repl ts typescript

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Namespace for REPL driven development for TypeScript/JavaScript

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README 

        
# repl-ns



Namespace for REPL driven development for TypeScript/JavaScript. 

Inspired by Clojure namespaces.

Currently tested on Node.js, but potentially can be used on any JavaScript runtime (Deno, Bun, Browser and so on...)



### Why REPL driven development?



*TL;DR Because it fastest, glad and fun way to develop software. Clojure guys approve it*



Node.js development process evolved gradually. At the beginning was nothing, and developers restarted node.js from scratch manually for code testing.

Then some automation appears [nodemon](https://nodemon.io/). Fine! Now I can relax from boring `Ctrl+C` -> `UP` -> `Enter` process. But it's not enough! Restarting node.js process from scratch is very expensive! 

* Need to require in runtime all project files. Yes! All this hundreds files of your 3+ years old monolith 😊

* Seems you have TypeScript too. Need to transpile all this kind with additional time wasting (Yeah! Say hello to ts-node perf tweak and all new TypeScript compilers, which written on Rust/C++/Go 😀)

* And establish DB connection too

* And establish Kafka/RabbitMQ/SQS connection too

* And establish Redis connection too

* And start HTTP server too



☝️ And all this seconds wasting process for just testing one line of code, that I change?


Maybe better "restart" one function instead whole process, where this line of code was changed?



### How to use (example)



Run your node.js program with `--inpsect` flag. Exposed inspect protocol will be used for REPL driven development.



Then organize code in your project using REPL driven development friendly style:



*some-namespace.ts*



```ts

import { ns } from 'repl-ns';



export const someNS = ns('some-namespace', {

  fn() {

    return 1 + 1

  },

});

```



And call namespace related functions anywhere:



```ts

import { someNS } from 'src/some-namespace';



someNS().fn() // 2

```



Now you can replace `someNS.fn` implementation in runtime without restarting node.js process. 


Just edit *some-namespace.ts*



```ts

- return 1 + 1

+ return 2 + 2

```



and use, for example, [node-remote-repl](https://github.com/darky/node-remote-repl) - `node-remote-repl some-namespace.ts`


Now anywhere `someNS().fn() // will return 4`


BTW, setup IDE for REPL driven development [VSCode example](https://github.com/darky/node-remote-repl#integration-with-ide)



Awesome! 🦄 Now fastest REPL driven development with node.js at your fingertips 



### Detailed example



```ts

import { ns } from 'repl-ns';



export const someNS = ns('some-namespace', {

  fn() {

    return 1 + 1 // functions always will be replaced in REPL

  },

  

  obj: {foo: 'bar'} // objects will be preserved in REPL by default (for stateful)

}, {

  forceRewrite: true, // if you want force replace objects too, this option will be helpful

  rewriteKeys: ['obj'], // or you can pick specific items for replacing

  async before(props) {

    // optional before hook namespace initialization

    // old namespace payload will be passed in props (if exists)

    // here you can close DB connection, stop HTTP server and so on

  },

  async after(props) {

    // optional after hook namespace initialization

    // new namespace payload will be passed in props

    // here you can establish DB connection, start HTTP server and so on

  },

  sync: true // pass sync: true if your namespace has totally sync behaviour

});



await someNS.ready // promise for ready state of namespace (before, after hooks executed yet)

```



### Real projects used repl-ns



You can explain code of projects:



* [ytdl-tui](https://github.com/darky/ytdl-tui) - TUI for downloading YouTube videos, totally writen with REPL driven development approach using **repl-ns**



### Caveats



Avoid using relative paths in your project:



```ts

import { someNS } from '../../some-namespace';

```



Because REPL code is run in root and can't detect relative paths



Use non-relative paths instead:



```ts

import { someNS } from 'src/some-namespace';

```



Projects, which helps with non-relative paths:

* [tsconfig-paths](https://github.com/dividab/tsconfig-paths)

* [tsc-alias](https://github.com/justkey007/tsc-alias)