bmeck

If you have ever had to deal with Promise heavy code, and in particular deep data structures you will likely be familiar with code like the following:

const body = await (await fetch(url)).json()

This has a LHS RHS interchange that causes non-linear edits while writing code (especially with autocomplete):

fetch(url) // LTR

bmeck

/// <reference types="node" />
// See NOTES below

import flatstr from 'flatstr'
import v8 from 'v8'

// @ts-check
class ArrayOfObjects {
  store = []
  constructor(count) {

bmeck

// node [--trace-gc] local-storage-exmaple.cjs
// creates a server
// will drop /favicon.ico connections poorly without properly closing them
//   `cleanupContext` AsyncLocalStorage + `cleanup` FinalizationRegistry will clean up
// will track the http request URL for errors in httpContext
//   will show up in error generated for bad permissions
// will grant permissions in permissionsContext based upon query params / search params
//   need ?fs=true to make / respond with a 200
//
// goto /?fs=true in browser to see it work

bmeck

// node [--trace-gc] local-storage-exmaple.cjs
// creates a server
// will drop /favicon.ico connections poorly without properly closing them
//   `cleanupContext` AsyncLocalStorage + `cleanup` FinalizationRegistry will clean up
// will track the http request URL for errors in httpContext
//   will show up in error generated for bad permissions
// will grant permissions in permissionsContext based upon query params / search params
//   need ?fs=true to make / respond with a 200
//
// goto /?fs=true in browser to see it work

bmeck

import util from 'util';
const promiseDebugging = util.debuglog('promises').enabled;
const danglingPromise = new FinalizationRegistry((stack) => {
  danglingStacks.delete(stack);
  console.log(stack);
});
const danglingStacks = new Set();
const stackCache = new WeakMap();
/**
 * @template T

bmeck

import * as ns from './index.js';
import {promisify} from 'util';
import {createReadStream, createWriteStream} from 'fs';
import {Session} from 'inspector';
import {PassThrough} from 'stream';
import {createHash} from 'crypto';

const session = new Session();
const stream = new PassThrough();

bmeck

#!/usr/bin/env node
// call using --inspect brk, GC using memory tab of devtools
// call globalThis.tick() to move the code along and see when things reap from
// manually calling GC
{
  const registry = new FinalizationRegistry((_) => console.log(_, 'reaped'));
  let EASY_TO_FIND = class EASY_TO_FIND2 {
    big = new Uint8Array(1024 * 1024 * 10);
    constructor(_) {
      registry.register(this, _);

bmeck

function foo(x, y) {
  return Object;
}
const { stop } = trace();
new foo([1], new Date());
stop();


// boilerplate after this

bmeck

# see the replacement character ( Buffer.from(new TextEncoder().encode('\u{fffd}')) ) instead
# https://en.wikipedia.org/wiki/Specials_(Unicode_block)#Replacement_character
node -e 'process.stdout.write("👌"[0]);setTimeout(() => {process.stdout.end("👌"[1]); process.exit()},3e3)' |
  node -e '(async (s = "") => {for await (const a of process.stdin) {console.log(a); s+= a}; console.log(s)})()'

bmeck

{
  "type": "object",
  "title": "Node.js Policy Manifest",
  "description": "https://nodejs.org/api/policy.html",
  "definitions": {
    "cascade": {
      "defaultSnippets": [
        {
          "label": "Allow scope fall through.",
          "body": true