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https://github.com/momothepug/tsmodule-alias

Nodejs Typescript path register
https://github.com/momothepug/tsmodule-alias

dynamic-aliases nodejs path-resolution tsmodule-alias typescript typescript-library typescript2

Last synced: 30 days ago
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Nodejs Typescript path register

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# tsmodule-alias



[![NPM Version][npm-image]][npm-url]



> **NOTE:** Before using any library for aliasing, try to improve your code structure as described [here](https://github.com/Microsoft/TypeScript/issues/9259#issuecomment-379305730) and [here](https://github.com/Microsoft/TypeScript/issues/9259#issuecomment-379372041).



> **NOTE:** Help me improve this project by reporting any issue.



Adds to Node module loader any alias defined in a Typescript configuration file. An example is available at https://github.com/momoThePug/tsmodule-alias-example



## Install



```

npm i --save @momothepug/tsmodule-alias

```



## Usage



Add these lines to your app's main file, before any code:



**Option A - Alias from Typescript file**



```js

// www.js, index.js, main.js, etc

const TSModuleAlias = require("@momothepug/tsmodule-alias");

// Path from package.json to your tsconfig.json file

const tsconfigToReadFromRoot = "./";

// Makes it work with play method

const aliasRegister = TSModuleAlias.play(tsconfigToReadFromRoot);

// Alias map loaded to nodejs from typescript paths (optional)

console.log(aliasRegister.nodeRegister.aliasMap);

// Displays root module and typescript project path (optional)

console.log(aliasRegister.currentEnvironmentData);

```



**Option B - Alias from Typescript file With custom aliases**



```js

// www.js, index.js, main.js, etc

const TSModuleAlias = require("@momothepug/tsmodule-alias");

// Path from package.json to your tsconfig.json file

const tsconfigToReadFromRoot = "./";

// Makes it work with play method, merging custom aliases

const aliasRegister = TSModuleAlias.play(tsconfigToReadFromRoot, {

  "@crazyAlias": __dirname + "/path/to/my/object"

});

// Alias map loaded to nodejs from typescript paths (optional)

console.log(aliasRegister.nodeRegister.aliasMap);

// Displays root module and typescript project path (optional)

console.log(aliasRegister.currentEnvironmentData);

```



**Option C - Dynamic aliases on the fly for development purpose**



You can override an alias value or define a new alias on runtime by invoking `addPathAlias("alias", "/path/to/your/module")` just like in our example:



```js

// www.js, index.js, main.js, etc

const TSModuleAlias = require("@momothepug/tsmodule-alias");

// Path from package.json to your tsconfig.json file

const tsconfigToReadFromRoot = "./";

// Makes it work with play method

const aliasRegister = TSModuleAlias.play(tsconfigToReadFromRoot);

// Defining/overriding an alias programatically, path value must be an absolute path

aliasRegister.addPathAlias(

  "@my_dynamic_alias",

  __dirname + "/leo/orange/dog/orange"

);

```



**Option D - Dynamic aliases on the fly**



You can register aliases using an object like the following example:



```js

const tSModuleAlias = require("@momothepug/tsmodule-alias");



// make it work using custom alias before execution

const aliasRegister = tSModuleAlias.use({

  "@leoAlias": __dirname + "/leo/orange/dog/orange",

  "@pugpath/pug": __dirname + "/myfooobar/func",

  "@bar": __dirname + "/bar/bar"

});



console.log(require("@bar"));

console.log(require("@pugpath/pug")("Jhon Doe"));

console.log(require("@leoAlias"));

```



**Option E - Alias register resolving tsconfig automatically**



You can initialize typescript alias, resolving tsconfig file automatically:



```js

// www.js, index.js, main.js, etc

const TSModuleAlias = require("@momothepug/tsmodule-alias");

// Makes it work with playAuto method

// this method Will scan backward until tsconfig is found

const aliasRegister = TSModuleAlias.playAuto(__dirname);

```



## Path resolution strategy



Only index zero will be used for path resolution in any alias definition. Ej:



```js

//  tsmodule-alias will resolve @root/* as "./src/*"

"@root/*": ["./src/*", "./moresrc/*", "./momosrc/*"]

```



## Nodejs & Typescript problem background



To avoid the path hell in typescript like the following example:



```typescript

import { MyClass } from "../../../my/own/module";

```



We can define aliases in tsconfig.json file using "paths" & "baseUrl" indexes:



```json

{

  "compilerOptions": {

    "target": "es6",

    "module": "commonjs",

    "outDir": "./",

    "strict": false,

    "baseUrl": "./",

    "declaration": true,

    "experimentalDecorators": true,

    "emitDecoratorMetadata": true,

    "paths": {

      "@root/*": ["./src/*"],

      "@test/*": ["./src/test/*"],

      "@mybeautifulModule": ["./src/modules/my/module"],

      "@deepmodule": ["./../../../my/own/module"]

    }

  },

  "include": ["./", "src/**/*"],

  "exclude": ["node_modules", "dist"]

}

```



That way we can use our aliases in any import:



```typescript

import { MyClass } from "@deepmodule";

```



**But...**



There is a problem when you compile a typescript project to be consumed by a Node interpreter: Node cannot understand what the hell are typescript **Path Aliases**!. To solve that you can use tsmodule-alias to read and load aliases from your tsconfig file.



**Nodejs Error thrown by the interpreter (example)**



```

   module.js:471

    throw err;

    ^



Error: Cannot find module '@CrazyAliasDefinedInTypescriptAliasConfig'

    at Function.Module._resolveFilename (module.js:469:15)

    at Function.Module._load (module.js:417:25)

    at Module.require (module.js:497:17)

    at require (internal/module.js:20:19)

    at Object. (/home/youruser/crazy/path/you-mod/index.js:7:13)

    at Module._compile (module.js:570:32)

    at Object.Module._extensions..js (module.js:579:10)

    at Module.load (module.js:487:32)

    at tryModuleLoad (module.js:446:12)

    at Function.Module._load (module.js:438:3)



npm ERR! CrazyOS 4.14.14-200.fc26.x86_64

npm ERR! argv "/usr/bin/node" "/usr/bin/npm" "run" "start"

npm ERR! node v6.12.0

npm ERR! npm  v3.10.10

npm ERR! code ELIFECYCLE

npm ERR! [email protected] start: ` npm run build && node index.js `

npm ERR! Exit status 1

npm ERR!

npm ERR! Failed at the [email protected] start script ' npm run build && node index.js '.

npm ERR! Make sure you have the latest version of node.js and npm installed.

npm ERR! If you do, this is most likely a problem with the you-mod package,

npm ERR! not with npm itself.

npm ERR! Tell the author that this fails on your system:

npm ERR!      npm run build && node index.js

npm ERR! You can get information on how to open an issue for this project with:

npm ERR!     npm bugs you-mod

npm ERR! Or if that isn't available, you can get their info via:

npm ERR!     npm owner ls you-mod

npm ERR! There is likely additional logging output above.



npm ERR! Please include the following file with any support request:

npm ERR!     /home/youruser/crazy/path/you-mod/npm-debug.log

```



:p Be happy



[npm-image]: https://img.shields.io/npm/v/@momothepug/tsmodule-alias.svg

[npm-url]: https://npmjs.org/package/@momothepug/tsmodule-alias