We make JSLab, a JavaScript and TypeScript scratchpad for Mac, so this is show-and-tell, not a review.

The video shows one rule: every result lands beside the line that made it.

You type, and Auto Run executes the tab on Bun a moment after you stop (300 ms by default). Each value, log and error is tagged with its source line, and clicking a row jumps to that line. There's no project to create and no build step.

Two ways to see a value without writing console.log:

const orders = [40, 15, 0]; const paid = orders.filter((total) => total > 0); paid //? // a magic comment shows this value paid.length // Auto Log: a top-level expression logs itself 

Docs: Your first tab · The output panel

JSLab launches Nov 15 for Apple Silicon Macs (macOS 14 or later), with a 14-day free trial: https://js-lab.app