@babel/plugin-transform-numeric-separator

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

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

// 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

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

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

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

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