RunJS Blog
runjs.app · Company blog · on HN since 2021
The maker of RunJS, a desktop JavaScript and TypeScript playground, writes about the app plus math and music theory for programmers.
What HN saysUsers say they use RunJS to prototype quickly without browser, npm or project setup; one reports a Paddle payment problem when buying it.
16HN people shared it
9linked it in comments
11stories submitted
24story points
2 months agolast shared
2021people per year2026
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What HN people wrote when they linked it
iKlsR · 2022-07-25
Great advice, that's why I bought https://runjs.app/ (not affiliated), I can quickly prototype pretty much anything with this and then port it to my actual target lang/framework after. Not hampered by the browser, npm, project setup or privacy concerns.
newsbinator · 2021-12-28
Last week I tried to buy RunJS (http://runjs.app), which uses Paddle. It wouldn't take my business credit card, so I emailed the creator. He said it's a Paddle problem and gave me Paddle's email.
I sent Paddle an email explaining what I was trying to buy, with a screenshot of the payment modal and error message, and their reply was an email bot that said:
> I wasn't able to tell exactly which transaction you're referring to, but it looks like your email **** is linked to a purchase of Unlimited icons pack from Icon54 on *** ** 2017 for USD 0 (order number ######).
> If you need further assistance with this purchase, you can follow this link to chat with me, Kino. I'm a virtual assistant, available 24/7 to help you with this matter.
I emailed this reply to the creator of RunJS and asked him to follow up with Paddle to help me buy his software.
His response was:
> I'd recommend following the instructions that Paddle provided.
> I'm, unfortunately, not able to assist with payment issues.
So my takeaway is yes: payments are broken, especially with Paddle. Payments would be less broken if anybody along the chain cared enough about support to solve payment problems.
lukehaas · 2024-12-11
I built https://runjs.app because I wanted an easy way to run JavaScript and test out ideas. It turned out that a lot of other people wanted the same thing.
The first version was free and very basic. After getting a lot of suggestions and feedback from the people using it, I added more features and introduced a freemium pricing model.
swah · 2024-07-03
Me too - I currently use https://runjs.app/ while developing but this would fit better.
unsupp0rted · 2022-04-22
I use the browser's dev console to try out short JS snippets or for simple on-page scraping. (for longer JS as a scratchpad I use https://runjs.app).
The browser's dev console gives you access to the current page's DOM, plus anything you can do in JS.
So stuff like `document.querySelectorAll(".foo")` works. Also `fetch()` works within the page's context.
Apart from that, what are some other useful things one can do in the dev console?
petercooper · 2021-07-21
https://runjs.app/ is also another player in this area, though is its own editor.
lockyc · 2023-12-23
have you tried RunJS? https://runjs.app/
traspler · 2022-02-21
To try out simple things I like to use https://runjs.app/
ameliaquining · 2025-07-14
At least in V8, this is not the case. To prove it, start a Chromium-based browser with the command-line flag --js-flags=--expose-gc, then go to https://runjs.app/play/#aWYgKCF3aW5kb3cuZ2MpIHsKICB0aHJvdyBuZXcgRXJyb3…