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@babel/plugin-transform-numeric-separator

info

This plugin is included in @babel/preset-env, in ES2021

Example​

Decimal Literals​

JavaScript
let budget = 1_000_000_000_000;

// What is the value of `budget`? It's 1 trillion!
//
// Let's confirm:
console.log(budget === 10 ** 12); // true

Binary Literals​

JavaScript
let nibbles = 0b1010_0001_1000_0101;

// Is bit 7 on? It sure is!
// 0b1010_0001_1000_0101
//             ^
//
// We can double check:
console.log(!!(nibbles & (1 << 7))); // true

Hex Literal​

JavaScript
// Messages are sent as 24 bit values, but should be
// treated as 3 distinct bytes:
let message = 0xa0_b0_c0;

// What's the value of the upper most byte? It's A0, or 160.
// We can confirm that:
let a = (message >> 16) & 0xff;
console.log(a.toString(16), a); // a0, 160

// What's the value of the middle byte? It's B0, or 176.
// Let's just make sure...
let b = (message >> 8) & 0xff;
console.log(b.toString(16), b); // b0, 176

// What's the value of the lower most byte? It's C0, or 192.
// Again, let's prove that:
let c = message & 0xff;
console.log(c.toString(16), b); // c0, 192

Octal Literal​

hand wave emoji

Octals are great for permissions, but also look better when represented in 0o0000 form. No real benefit with separators here.

Installation​

npm install --save-dev @babel/plugin-transform-numeric-separator

Usage​

babel.config.json
{
  "plugins": ["@babel/plugin-transform-numeric-separator"]
}

Via CLI​

Shell
babel --plugins @babel/plugin-transform-numeric-separator script.js

Via Node API​

JavaScript
require("@babel/core").transformSync("code", {
  plugins: ["@babel/plugin-transform-numeric-separator"],
});

Additional Information​

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" plugin:

info

@babel/plugin-transform-literals is already included in @babel/preset-env.

babel.config.json
{
  "presets": ["@babel/preset-env"],
  "plugins": ["@babel/plugin-transform-numeric-separator"]
}
{
  "plugins": ["@babel/plugin-transform-numeric-separator", "@babel/plugin-transform-literals"]
}

References​