maxvien / supermemo

🧑‍🎓 A JavaScript/TypeScript implementation of the SuperMemo 2 (SM2) algorithm for spaced based repetition flashcards.

SuperMemo

A JavaScript/TypeScript implementation of the SuperMemo 2 (SM2) algorithm for spaced based repetition flashcards.

Hit the Star button if you love this project ⭐️

Explanation

type SuperMemoItem = {
  interval: number;
  repetition: number;
  efactor: number;
};

type SuperMemoGrade = 0 | 1 | 2 | 3 | 4 | 5;

supermemo(item: SuperMemoItem, grade: SuperMemoGrade): SuperMemoItem

• item
  • repetition: the number of continous correct responses. The initial repetition value should be 0.
  • interval: inter-repetition interval after the repetitions (in days). The initial interval value should be 0.
  • efactor: easiness factor reflecting the easiness of memorizing and retaining a given item in memory. The initial efactor value should be 2.5.
• grade:
  • 5: perfect response.
  • 4: correct response after a hesitation.
  • 3: correct response recalled with serious difficulty.
  • 2: incorrect response; where the correct one seemed easy to recall.
  • 1: incorrect response; the correct one remembered.
  • 0: complete blackout.

Installation

For Webpack

npm install --save supermemo

import { supermemo, SuperMemoItem, SuperMemoGrade } from 'supermemo';

For Node

npm install --save supermemo

const { supermemo } = require('supermemo');

For Deno

import { supermemo, SuperMemoItem, SuperMemoGrade } from 'https://deno.land/x/supermemo/mod.ts';

Usage

let item: SuperMemoItem = {
  interval: 0,
  repetition: 0,
  efactor: 2.5,
};

console.log(item);

item = supermemo(item, 5);
console.log(item);

item = supermemo(item, 4);
console.log(item);

How to implement SuperMemo with DayJS?

import dayjs from 'dayjs';
import { supermemo, SuperMemoItem, SuperMemoGrade } from 'supermemo';

interface Flashcard extends SuperMemoItem {
  front: string;
  back: string;
  dueDate: string;
}

function practice(flashcard: Flashcard, grade: SuperMemoGrade): Flashcard {
  const { interval, repetition, efactor } = supermemo(flashcard, grade);

  const dueDate = dayjs(Date.now()).add(interval, 'day').toISOString();

  return { ...flashcard, interval, repetition, efactor, dueDate };
}

let flashcard: Flashcard = {
  front: 'programer',
  back: 'an organism that turns caffeine in software',
  interval: 0,
  repetition: 0,
  efactor: 2.5,
  dueDate: dayjs(Date.now()).toISOString(),
};

console.log(flashcard);

flashcard = practice(flashcard, 5);
console.log(flashcard);

flashcard = practice(flashcard, 3);
console.log(flashcard);

References

• The explanation of SuperMemo 2 Algorithm
• The Delphi implementation of SuperMemo 2 Algorithm

supermemo's Issues

It doesn't work with Deno

Hi, thank you for making it publicly available! I tried to use it with Deno, but even only import doesn't work. Am I missing something?

$ deno -V
deno 1.16.2

$ cat index.ts
import { supermemo, SuperMemoItem, SuperMemoGrade } from 'https://deno.land/x/supermemo/mod.ts';

$ deno run -A index.ts
Check file:///Users/kyanny/workspace/sm2/index.ts
thread 'main' panicked at 'internal error: entered unreachable code: unexpected missing emit: https://deno.land/x/[email protected]/mod.ts', cli/proc_state.rs:544:15
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

$ RUST_BACKTRACE=full deno run -A index.ts
Check file:///Users/kyanny/workspace/sm2/index.ts
thread 'main' panicked at 'internal error: entered unreachable code: unexpected missing emit: https://deno.land/x/[email protected]/mod.ts', cli/proc_state.rs:544:15
stack backtrace:
   0:        0x10ba63d3f - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hf1ee81583766da09
   1:        0x10b3299fb - core::fmt::write::h8dc218a6eb2426a8
   2:        0x10ba6221a - std::io::Write::write_fmt::heef3e26d448f8c80
   3:        0x10ba62e95 - std::panicking::default_hook::{{closure}}::h4b7de73863cf8582
   4:        0x10ba625f7 - std::panicking::default_hook::h778da672ce56a579
   5:        0x10b2e5106 - deno::setup_exit_process_panic_hook::{{closure}}::hfe9a9204138a8142
   6:        0x10ba620c9 - std::panicking::rust_panic_with_hook::ha5146542f697c8af
   7:        0x10ba830ea - std::panicking::begin_panic_handler::{{closure}}::hd8bf1442c82bf304
   8:        0x10ba83069 - std::sys_common::backtrace::__rust_end_short_backtrace::h73a3d0f5ab35b08b
   9:        0x10ba83025 - _rust_begin_unwind
  10:        0x10cc46f5f - core::panicking::panic_fmt::h16f19dd104182e80
  11:        0x10b09de07 - deno::proc_state::ProcState::prepare_module_load::{{closure}}::h7ff3d5c5a5f7f040
  12:        0x10b09b6be - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h95f4f81560e11b4e
  13:        0x10b09b4ad - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hba28f970eba75693
  14:        0x10afb5426 - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h011315fb8be13289
  15:        0x10afb41a9 - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h1d99aa03600e7c07
  16:        0x10b0c1591 - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hac80c5777a31e8a2
  17:        0x10b0bef04 - deno::run_command::{{closure}}::h26541ce94df71d31
  18:        0x10b0bdb61 - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h95b64f207b752c8f
  19:        0x10af8b2e7 - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hcd0e8c40af4c0e1c
  20:        0x10af7c929 - deno::main::heb40db0691ea69e2
  21:        0x10af7824c - std::sys_common::backtrace::__rust_begin_short_backtrace::h88e6039fee8e0e1b
  22:        0x10af784a0 - _main

SM-xx

Hi, glad to see you implement the SM2, I was always hoping there can be a ts writted srs library.

Currently we are using https://github.com/open-spaced-repetition/fsrs.js in https://github.com/oflg/fishing in https://github.com/tiddly-gittly/TidGi-Desktop , the fsrs is based on SM17 but is originally designed. Maybe you can get some inspiration and implement SM-10+ with it.

Add previous flashcard interval in practice function

Hi :)

I haven't read the SM-2 spec or anything, but shouldn't it be interval + flashcard.interval in the How to implement SuperMemo with DayJS? section of the README?

  const dueDate = dayjs(Date.now())
    .add(interval + flashcard.interval, 'day')
    .toISOString();

Otherwise, you're only ever adding the last interval to today's date.

Thanks

Shouldnt calling supermemo with a poor grade keep the interval as 0?

Hey all
In this example

let flashcard: Flashcard = {
  front: 'programer',
  back: 'an organism that turns caffeine in software',
  interval: 0,
  repetition: 0,
  efactor: 2.5,
  dueDate: dayjs(Date.now()).toISOString(),
};

console.log(flashcard);

flashcard = practice(flashcard, 1);
console.log(flashcard);

I would expect the dueDate for the flashcard to continue to be today's date, since the grade was 1 (incorrect response). In other words, I'd expect the card to remain due until the user selects 3/4/5 as the grade. At least thats is my expectation as an Anki user. Am I mistaken about how Supermemo algorithm works or am I misunderstanding something?

Thank you

Simple JS version for browser use

Is there any chance you could provide a simple JS version for browser use where webpack etc. are not available?