JavaScriptを定義する。

#!/usr/bin/env node
// in the Module Goal
export {};
console.log(1);

new Worker("foo.wasm", { type: "module", assert: { type: "webassembly" } });

import json from "./foo.json" assert { type: "json" };

// See the repo for detailed examples. // small example from the cook book
const date = Temporal.now.plainDateISO(); // Gets the current date
date.toString(); // returns the date in ISO 8601 date format
// If you additionally want the time
Temporal.now.plainDateTimeISO().toString(); // date and time in ISO 8601 format

// Resizable ArrayBuffer

let rab = new ArrayBuffer(1024, { maximumByteLength: 1024 ** 2 });
assert(rab.byteLength === 1024);
assert(rab.maximumByteLength === 1024 ** 2);
assert(rab.resizable);
rab.resize(rab.byteLength * 2);
assert(rab.byteLength === 1024 * 2);

// Transfer the first 1024 bytes.
let ab = rab.transfer(1024);

// rab is now detached
assert(rab.byteLength === 0);
assert(rab.maximumByteLength === 0);

// The contents are moved to ab.
assert(!ab.resizable);
assert(ab.byteLength === 1024);

const array = [{ value: 1 }, { value: 2 }, { value: 3 }, { value: 4 }];
array.find(n => n.value % 2 === 1); // { value: 1 }
array.findIndex(n => n.value % 2 === 1); // 0

const red = new ShadowRealm();

// realms can import modules that will execute within it's own environment.
// When the module is resolved, it captured the binding value, or creates a new
// wrapped function that is connected to the callable binding.
const redAdd = await red.importValue('./inside-code.js', 'add');

// redAdd is a wrapped function exotic object that chains it's call to the
// respective imported binding.
let result = redAdd(2, 3);

const array = [1, 2, 3, 4, 5];

// groupBy groups items by arbitrary key.
// In this case, we're grouping by even/odd keys
array.groupBy((num, index, array) => {
  return num % 2 === 0 ? 'even': 'odd';
});

// =>  { odd: [1, 3, 5], even: [2, 4] }

// groupByToMap returns items in a Map, and is useful for grouping using
// an object key.
const odd  = { odd: true };
const even = { even: true };
array.groupByToMap((num, index, array) => {
  return num % 2 === 0 ? even: odd;
});

// =>  Map { {odd: true}: [1, 3, 5], {even: true}: [2, 4] }