Show HN: I made a web-based notepad with a built in unit calculator

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  • decimal.js

    An arbitrary-precision Decimal type for JavaScript

    Looks good! I love the idea of the embedded calculator

    I noticed that it doesn't handle remainder/modulo (%) equations:

    "10 % 2" results in: "Left hand side of addition cannot be a percentage."

    It does look like decimal.js can handle that:

  • notecalc3

    NoteCalc is a handy calculator trying to bring the advantages of Soulver to the web.

    Very cool!

    This reminds me of the open source NoteCalc:

    It was discussed on HN, you might look there for inspiration:

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    Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.

  • numi

    Beautiful calculator app for macOS

    Very nice! Reminds me a lot of numi ( Similar, but MacOS only (and paid).

  • recomputer

    A smart calculator web app

  • CalcPad

    A different take on the caculator (by filipesabella)

    I've made this one and use it daily:

    It's electron though, if that's important to you.

  • human_calc

    Calculator that processes formulas like a human

    Along the same lines, I made a command line calculator that does basic unit conversions, and has a few other tricks up it's sleeve

    I find it surprisingly useful. It's probably one of those things that has an audience of one, but I find it useful.

  • insect

    High precision scientific calculator with support for physical units

  • WorkOS

    The modern API for authentication & user identity. The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.

  • mathjs

    An extensive math library for JavaScript and Node.js

    Ha, yes, I was being nosy. It was quite easy to spot as it's the only XHR/Fetch request.

    I was intrigued what you had used to build it, and if you had built your own solver (which you have), and what editor you used (Code Mirror) so went looking at the code. Interesting to see you left the source maps for production, made it easy for my sleuthing...

    I experimented with a similar idea last year, but used ProseMirror/TipTap as the editor to enable rich text editing, and the MathJS ( solver. I also combined it with PouchDB and Yjs for offline editing and syncing between devices. Never finished it though, you have kept your nice and simple!

  • eulalie

    ES6 flavoured parser combinators

  • MarkdownFormula

    Use Excel-like formulas in markdown tables

  • moo

    Optimised tokenizer/lexer generator! 🐄 Uses /y for performance. Moo. (by no-context)

  • redbean-calcpad

    CalcPad served with redbean

    I wanted to see how this would run in redbean[1], and it runs fantastically!

    If you wanna see this in a little executable that you can pass around to your friends, check out this repo I threw up:


  • Joplin

    Joplin - the secure note taking and to-do app with synchronisation capabilities for Windows, macOS, Linux, Android and iOS.

    That's really cool!

    Anyone knows if there's a way to have this feature in Joplin[0] ?


  • note-parser

    A plain-text parser (in early stages).


    It's still in development. I built a proof-of-concept from scratch almost a year ago, which I just open-sourced at the following link.

    I intend to develop it a bit more and host it online.

    A previous prototype, really barebones, is at

    The idea is to drag and drop (or type) a plain-text note and visualize the data as a scatterplot or other charts.

  • SoulverCore

    A powerful Swift framework for evaluating natural language math expressions

  • libqalculate

    Qalculate! library and CLI

    Note: I had this response typed up but didn't submit...

    One related app that I absolutely love is Qalculate![1] (yes, it has a built-in exclamation for default enthusiasm :) )

    It can do cool stuff like converting N (newtons) to kg.m/s^2 when you specify units as ?kg. It also converts units like 1kW x 1year = 31.55... GJ

    It's fantastic for engineering and specially back-of-envelope calculations. This notepad aspect does seem useful though. One alternative is to use Jupyter notebooks, sometimes I work problems with Sage[2]+Jupyter. Sage is extremely powerful (you can do calculus, linear algebra, and more) but doesn't support units (that I know of), it's more geared toward advanced maths.


    [2] It's a bit on the heavy side although it's definitely worth it if you're doing a lot of math. I think the flatpak is preferred due to its significant size.

  • liveCalc

    having fun with arithmetic


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