webdev_notes

Short runnable JavaScript snippets on classic interview topics. Each note is a single file — run it with Node and compare the output with what you expected.

Notes

Note	What it demonstrates
closures/closures.js	A returned function keeps access to its outer scope; a function factory that adds a fixed number
event_loop/event_loop.js	Order of synchronous code, promise callbacks and setTimeout
macrotasks_microtasks/macrotasks_microtasks.js	Which queue setTimeout, setInterval, setImmediate, process.nextTick, Promise.then and queueMicrotask go to, and the resulting order
let_vs_var/let_vs_var.js	Function vs block scope, redeclaration, and the classic var in a loop with setTimeout (plus the closure fix)
reduce/reduce.js	Array.prototype.reduce summing an array

Run

Any recent Node.js works, no dependencies:

node closures/closures.js
node event_loop/event_loop.js
node let_vs_var/let_vs_var.js
node reduce/reduce.js
node macrotasks_microtasks/macrotasks_microtasks.js   # keeps running (setInterval) — stop with Ctrl+C

For example, event_loop.js prints 3, 4, 2, 2.5, 1: synchronous code first, then all microtasks, then the timer.

Written in July–August 2023.

License

MIT (as declared in package.json).