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https://github.com/kimamula/ts-transformer-keys
A TypeScript custom transformer which enables to obtain keys of given type
https://github.com/kimamula/ts-transformer-keys
Last synced: 8 days ago
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A TypeScript custom transformer which enables to obtain keys of given type
- Host: GitHub
- URL: https://github.com/kimamula/ts-transformer-keys
- Owner: kimamula
- License: mit
- Created: 2017-04-22T06:23:22.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2024-06-18T06:26:30.000Z (10 days ago)
- Last Synced: 2024-06-18T12:38:53.121Z (10 days ago)
- Language: TypeScript
- Homepage:
- Size: 919 KB
- Stars: 769
- Watchers: 8
- Forks: 84
- Open Issues: 15
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# ts-transformer-keys
A TypeScript custom transformer which enables to obtain keys of given type.
[![NPM version][npm-image]][npm-url]
[](https://www.npmjs.com/package/ts-transformer-keys)
# Requirement
TypeScript >= 2.4.1
# How to use this package
This package exports 2 functions.
One is `keys` which is used in TypeScript codes to obtain keys of given type, while the other is a TypeScript custom transformer which is used to compile the `keys` function correctly.
## How to use `keys`
```ts
import { keys } from 'ts-transformer-keys';
interface Props {
id: string;
name: string;
age: number;
}
const keysOfProps = keys();
console.log(keysOfProps); // ['id', 'name', 'age']
```
## How to use the custom transformer
Unfortunately, TypeScript itself does not currently provide any easy way to use custom transformers (See https://github.com/Microsoft/TypeScript/issues/14419).
The followings are the example usage of the custom transformer.
### webpack (with ts-loader or awesome-typescript-loader)
See [examples/webpack](examples/webpack) for detail.
```js
// webpack.config.js
const keysTransformer = require('ts-transformer-keys/transformer').default;
module.exports = {
// ...
module: {
rules: [
{
test: /\.ts$/,
loader: 'ts-loader', // or 'awesome-typescript-loader'
options: {
// make sure not to set `transpileOnly: true` here, otherwise it will not work
getCustomTransformers: program => ({
before: [
keysTransformer(program)
]
})
}
}
]
}
};
```
### Rollup (with rollup-plugin-typescript2)
See [examples/rollup](examples/rollup) for detail.
```js
// rollup.config.js
import resolve from 'rollup-plugin-node-resolve';
import typescript from 'rollup-plugin-typescript2';
import keysTransformer from 'ts-transformer-keys/transformer';
export default {
// ...
plugins: [
resolve(),
typescript({ transformers: [service => ({
before: [ keysTransformer(service.getProgram()) ],
after: []
})] })
]
};
```
### ttypescript
See [examples/ttypescript](examples/ttypescript) for detail.
See [ttypescript's README](https://github.com/cevek/ttypescript/blob/master/README.md) for how to use this with module bundlers such as webpack or Rollup.
```jsonc
// tsconfig.json
{
"compilerOptions": {
// ...
"plugins": [
{ "transform": "ts-transformer-keys/transformer" }
]
},
// ...
}
```
### ts-jest
See [examples/ts-jest](examples/ts-jest) for details.
In order to use this transformer with ts-jest, you need to add a wrapper around it like this:
```javascript
// ts-jest-keys-transformer.js
const keysTransformer = require('ts-transformer-keys/transformer').default;
const name = 'my-key-transformer';
const version = 1;
const factory = (cs) => (ctx) => keysTransformer(cs.program)(ctx);
// For ts-jest 26 use:
// const factory = (cs) => (ctx) => keysTransformer(cs.tsCompiler.program)(ctx);
module.exports = { name, version, factory };
```
And add it in `jest.config.js` like this:
```javascript
globals: {
'ts-jest': {
// relative path to the ts-jest-keys-transformer.js file
astTransformers: { before: ['src/react/ts-jest-keys-transformer.js'] },
},
},
```
Note: ts-jest 26.4.2 does not work with this transformer (fixed in ts-jest 26.4.3). Also, for versions smaller than 26.2, you need to provide the transformer in an array instead, like this: `astTransformers: { before: ['src/react/ts-jest-keys-transformer.js'] }`
### TypeScript API
See [test](test) for detail.
You can try it with `$ npm test`.
```js
const ts = require('typescript');
const keysTransformer = require('ts-transformer-keys/transformer').default;
const program = ts.createProgram([/* your files to compile */], {
strict: true,
noEmitOnError: true,
target: ts.ScriptTarget.ES5
});
const transformers = {
before: [keysTransformer(program)],
after: []
};
const { emitSkipped, diagnostics } = program.emit(undefined, undefined, undefined, false, transformers);
if (emitSkipped) {
throw new Error(diagnostics.map(diagnostic => diagnostic.messageText).join('\n'));
}
```
As a result, the TypeScript code shown [here](#how-to-use-keys) is compiled into the following JavaScript.
```js
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var ts_transformer_keys_1 = require("ts-transformer-keys");
var keysOfProps = ["id", "name", "age"];
console.log(keysOfProps); // ['id', 'name', 'age']
```
# Note
* The `keys` function can only be used as a call expression. Writing something like `keys.toString()` results in a runtime error.
* `keys` does not work with a dynamic type parameter, i.e., `keys()` in the following code is converted to an empty array(`[]`).
```ts
class MyClass {
keys() {
return keys();
}
}
```
# License
MIT
[npm-image]:https://img.shields.io/npm/v/ts-transformer-keys.svg?style=flat
[npm-url]:https://npmjs.org/package/ts-transformer-keys