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| --- | ||
| id: babel7-or-ts | ||
| title: Babel7 or TypeScript | ||
| --- | ||
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| In Sept. 2018 Babel7 got released with an interesting preset: `@babel/preset-typescript`. | ||
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| The goal is to make it easy for users using Babel to try TypeScript without moving out from Babel, just by adding a preset in their Babel config (here is the [MSDN blog post](https://blogs.msdn.microsoft.com/typescript/2018/08/27/typescript-and-babel-7/) about TypeScript and Babel 7). | ||
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| ## Limitations | ||
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| While `@babel/preset-typescript` is a great preset, you must know the limitation of it. Here is what is possible with TypeScript (and `ts-jest`), which is not with Babel7 and `@babel/preset-typescript`: | ||
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| #### No type-checking | ||
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| This is the big **PRO** of using TypeScript vs Babel, you have type-checking out of the box. | ||
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| You'll get a more fluent TDD experience (when using `ts-jest`) since files will be type-checked at the same time they're compiled and ran. | ||
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| Here TypeScript will throw while Babel won't: | ||
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| ```ts | ||
| const str: string = 42 | ||
| ``` | ||
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| With Babel, files are transpiled as isolated modules, there is no notion of "project". With TypeScript, files are part of a project and are compiled in that scope. | ||
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| --- | ||
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| #### No `namespace` | ||
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| ```ts | ||
| namespace app { | ||
| export const VERSION = '1.0.0' | ||
| export class App { | ||
| /* ... */ | ||
| } | ||
| } | ||
| ``` | ||
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| --- | ||
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| #### No `const enum` | ||
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| ```ts | ||
| const enum Directions { | ||
| Up, | ||
| Down, | ||
| Left, | ||
| Right, | ||
| } | ||
| ``` | ||
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| --- | ||
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| #### No declaration merging (`enum`, `namespace`, ...) | ||
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| You won't be able to do [declaration merging](https://www.typescriptlang.org/docs/handbook/declaration-merging.html). | ||
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| --- | ||
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| #### No legacy `import`/`export` | ||
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| ```ts | ||
| import lib = require('lib') | ||
| // ... | ||
| export = myVar | ||
| ``` | ||
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| --- | ||
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| #### No caret type-casting with JSX enabled | ||
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| ```ts | ||
| const val = <string>input | ||
| ``` |
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