Enable support for JS stage 4 features

[twokul]

Enables support for JS stage 4 features.

• Nullish Coalescing
• Numeric Separator
• Optional Catch Binding

Nullish Coalescing

const response = {
  settings: {
    nullValue: null,
    height: 400,
    animationDuration: 0,
    headerText: '',
    showSplashScreen: false
  }
};

const undefinedValue = response.settings.undefinedValue ?? 'some other default'; // result: 'some other default'
const nullValue = response.settings.nullValue ?? 'some other default'; // result: 'some other default'

Numeric Separator

1_000_000_000           // Ah, so a billion
101_475_938.38          // And this is hundreds of millions

let fee = 123_00;       // $123 (12300 cents, apparently)
let fee = 12_300;       // $12,300 (woah, that fee!)
let amount = 12345_00;  // 12,345 (1234500 cents, apparently)
let amount = 123_4500;  // 123.45 (4-fixed financial)
let amount = 1_234_500; // 1,234,500

0.000_001 // 1 millionth
1e10_000  // 10^10000

// Binary
let nibbles = 0b1010_0001_1000_0101;

// Hex Litral
let message = 0xA0_B0_C0;

// Octal Literal
let x = 0o1234_5670;

Optional Catch Binding

try {
  throwAnException();
} catch {
  console.log('we do not care about error object here, carry on');
}