115 lines
2.6 KiB
Markdown
115 lines
2.6 KiB
Markdown
# @babel/plugin-proposal-numeric-separator
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> This plugin allows Babel to transform Decimal, Binary, Hex and Octal literals containing Numeric Literal Separator to their non-separated form.
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## Example
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### Decimal Literals
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```js
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let budget = 1_000_000_000_000;
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// What is the value of `budget`? It's 1 trillion!
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//
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// Let's confirm:
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console.log(budget === 10 ** 12); // true
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```
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### Binary Literals
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```js
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let nibbles = 0b1010_0001_1000_0101;
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// Is bit 7 on? It sure is!
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// 0b1010_0001_1000_0101
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// ^
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//
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// We can double check:
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console.log(!!(nibbles & (1 << 7))); // true
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```
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### Hex Literal
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```js
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// Messages are sent as 24 bit values, but should be
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// treated as 3 distinct bytes:
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let message = 0xA0_B0_C0;
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// What's the value of the upper most byte? It's A0, or 160.
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// We can confirm that:
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let a = (message >> 16) & 0xFF;
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console.log(a.toString(16), a); // a0, 160
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// What's the value of the middle byte? It's B0, or 176.
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// Let's just make sure...
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let b = (message >> 8) & 0xFF;
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console.log(b.toString(16), b); // b0, 176
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// What's the value of the lower most byte? It's C0, or 192.
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// Again, let's prove that:
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let c = message & 0xFF;
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console.log(c.toString(16), b); // c0, 192
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```
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### Octal Literal
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*hand wave emoji*
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Octals are great for permissions, but also look better when represented in `0o0000` form. No real benefit with separators here.
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## Installation
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```sh
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npm install --save-dev @babel/plugin-proposal-numeric-separator
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```
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## Usage
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### Via `.babelrc` (Recommended)
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**.babelrc**
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```json
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{
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"plugins": ["@babel/plugin-proposal-numeric-separator"]
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}
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```
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### Via CLI
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```sh
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babel --plugins @babel/plugin-proposal-numeric-separator script.js
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```
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### Via Node API
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```javascript
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require("@babel/core").transform("code", {
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plugins: ["@babel/plugin-proposal-numeric-separator"]
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});
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```
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## Additional Information
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If you need to further compile ES2015 Decimal, Binary, Hex and Octal number representations to their pre-ES2015 numeric literal form, add the [`"@babel/plugin-transform-literals"`](http://babeljs.io/docs/plugins/transform-literals/) plugin:
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> `@babel/plugin-transform-literals` is already included in [@babel/preset-env](https://github.com/babel/babel/tree/master/packages/babel-preset-env) and @babel/preset-es2015.
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### Via `.babelrc` (Recommended)
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**.babelrc**
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```json
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{
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"presets": ["@babel/preset-env"],
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"plugins": ["@babel/plugin-proposal-numeric-separator"]
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}
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{
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"plugins": ["@babel/plugin-proposal-numeric-separator", "@babel/plugin-transform-literals"]
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}
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```
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## References
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* [Proposal: Numeric Separators](https://github.com/samuelgoto/proposal-numeric-separator)
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