bathos

// This is useful for a few things:
//
// 1. Checking what dictionary options are supported by some platform API.
// 2. Debugging mysterious cases where an object you pass as input to another
//    API doesn’t seem to get treated the way you’re expecting.
// 3. When designing another Proxy’s handler implementation, verifying that you
//    are accounting for everything correctly and that the intended abstraction 
//    isn’t leaking in quirky ways.
//
// ex:

bathos

// CLASS SYNTAX ////////////////////////////////////////////////////////////////

class AFoo {}
class ABar extends AFoo {}

// FUNCTION SYNTAX NEAR-EQUIV //////////////////////////////////////////////////

function BFoo() {
  if (!new.target) {
    throw new TypeError('Illegal constructor');

bathos

export default function acornSkullFishKoalaCaressingAndNonstopSpinalDraining(Parser) {
  const tt = Parser.acorn.tokTypes;
  const ocToken = new Parser.acorn.TokenType('?.');
  const ncToken = new Parser.acorn.TokenType('??', {
    beforeExpr: true,
    binop: 2.5
  });

  return class extends Parser {
    getTokenFromCode(codePoint) {

bathos

function matchAllButUpdateOriginalRegExp(regExp, string) {
  return regExp[Symbol.matchAll].call({
    constructor: { [Symbol.species]: function() { return regExp; } },
    flags: regExp.flags,
    lastIndex: regExp.lastIndex
  }, string);
}

const pattern = /./g;

bathos

class Foo extends Bar {
  method() {
    const homeObject = Foo.prototype;
    const superReferenceBase = Object.getPrototypeOf(homeObject);
  }

  static method() {
    const homeObject = Foo;
    const superReferenceBase = Object.getPrototypeOf(homeObject);
  }

bathos

Trying to understand what accounts for "\8" and "\9" being considered valid string literals with identity escapes in Chrome and FF.

Annex B permits sloppy mode to include legacy octal escapes in strings. It achieves this by replacing the ‘normal’ (strict) EscapeSequence production with a new version accompanied by three new productions.

• Strict: https://tc39.es/ecma262/#prod-EscapeSequence
• Sloppy: https://tc39.es/ecma262/#prod-annexB-EscapeSequence

In the sloppy version, three of the alternatives are the same. The change is replacing this rule:

"0" [lookahead ∉ DecimalDigit]

bathos

import range from '/util/iterator/range.mjs';

// Week start data pulled from similarly golfed answer on SO:
// https://stackoverflow.com/a/57102881/1631952
//
// I’m not thrilled with this; we probably ought to be generating it since the
// data is pretty obscure. OTOH I’d be far less thrilled with loading hefty
// chunks of ICU data and this is pretty solid and compact!
//
// Note that the RegExp given for lang tags in that answer is a bit off. The one

bathos

void async function() {
  const asyncGenerator = async function *() { try { yield; } catch {} }();

  try {
    for await (const value of asyncGenerator) {
      await asyncGenerator.throw(new Error);
    }

    console.log('caught');
  } catch {

bathos

FK	Cstr	TM: Lexical	TM: Global / Strict
normal	cstr	-	function() {}; new Function
normal	no	() => {}	x() {}
classConstructor	cstr	-	class {}
classConstructor	no	-	-
generator	cstr	-	-
generator	no	-	function * () {}; * x() {}
async	cstr	-	-
async	no	async () => {}	async function() {}; async x() {}

bathos

When Strings Attack

The Enduring Legacy of a Very Naughty Hack from 1995 / A Bit of Intl

This is my first attempt at a tech talk thing. The focus here is strings in ES. First we’ll talk about what a string is in ES, then some of the consequences that fall out of that (a few aren’t super obvious), and finally some of the cool tools available for working with strings safely & effectively. Because of the nature of the subject we’ll also get into some more general information about Unicode, encodings and broad concepts related to strings and language.