true-myth

A library for safe functional programming in JavaScript, with first-class support for TypeScript

MIT 86 个版本

typescript functional programming maybe result

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安装

npm install true-myth

yarn add true-myth

pnpm add true-myth

bun add true-myth

README

True Myth

True Myth provides safe, idiomatic null, error, and async code handling in TypeScript, with Maybe, Result, and Task types that are really nice.

README • API docs • Source • Intro blog post

Overview

True Myth provides standard, type-safe wrappers and helper functions to help you with three extremely common cases in programming:

not having a value
having a result where you need to deal with either success or failure
having an asynchronous operation which may fail

You could implement all of these yourself – it's not hard! – but it's much easier to just have one extremely well-tested library you can use everywhere to solve this problem once and for all.

See the docs for setup, guides, and API docs!

Requirements
Compatibility
Basic bundle size info

Requirements

TS 5.3+
tsconfig.json:
- moduleResolution: use "Node16" or later
- strict: true
package.json
- type: "module" (or else use import() to import True Myth into a commonJS build)

For details on using a pure ES modules package in TypeScript, see the TypeScript handbook's guide.

Compatibility

This project follows the current draft of the Semantic Versioning for TypeScript Types specification.

Currently supported TypeScript versions: 5.3–6.0
Compiler support policy: simple majors
Public API: all published, documented types not in a -private module and not marked as @internal or @private are public

Basic bundle size info

Size of the ESM build without tree-shaking (yes, these are in bytes: this is a pretty small library!):

file	size (B)	terser[^terser] (B)	terser and brotli[^brotli] (B)
-private/utils.js	942	358	175
index.js	644	352	122
maybe.js	23052	3838	943
result.js	21376	4257	1034
standard-schema.js	5984	758	318
task/delay.js	3901	649	259
task.js	59937	7629	2036
test-support.js	473	142	89
toolbelt.js	3739	886	278
unit.js	656	58	57
total[^total]	120704	18927	5311

Notes:

The unmodified size includes comments.
Thus, running through Terser gets us a much more realistic size: about 18.1KB to parse.
The total size across the wire of the whole library will be ~5.2KB.

This is all tree-shakeable to a significant degree: you should only have to “pay for” the types and functions you actually use, directly or indirectly. If your production bundle does not import or use anything from true-myth/test-support, you will not pay for it, for example. However, some parts of the library do depend directly on other parts: for example, toolbelt uses exports from result and maybe, and Task makes extensive use of Result under the hood.

In detail, here are the dependencies of each module:

Module	Depends on
`index.js`	All, but as tree-shakeable as possible
`maybe.js`	`unit.js`, `-private/utils.js`
`result.js`	`unit.js`, `-private/utils.js`
`standard-schema.js`	`task.js`, `result.js`
`task.js`	`result.js`, `unit.js`, `task/delay.js`, `-private/utils.js`
`task/delay.js`	None
`test-support.js`	`maybe.js`, `result.js`
`toolbelt.js`	`maybe.js`, `result.js`, `-private/utils.js`

This intentionally excludes the ESLint plugin contents, which should not be part of an production bundle.

[^terser]: Using terser 5.46.2 with --compress --mangle --mangle-props.

[^brotli]: Generated by running gzip -kq11 on the result of the terser invocation.

[^total]: This is just the sum of the previous lines. Real-world bundle size is a function of what you actually use, how your bundler handles tree-shaking, and how the results of bundling compresses. Notice that sufficiently small files can end up larger after compression; this stops being an issue once part of a bundle.

Inspiration

The design of True Myth draws heavily on prior art; essentially nothing of this is original – perhaps excepting the choice to make Maybe.of handle null and undefined in constructing the types. In particular, however, True Myth draws particular inspiration from:

Rust's Option and Result types and their associated methods
Folktale's Maybe and Result implementations
Elm's Maybe and Result types and their associated functions

版本列表

9.4.0 2026-05-25

9.3.1 2025-11-25

9.3.0 2025-11-25

9.2.0 2025-09-27

9.1.0 2025-08-25

9.0.1 2025-05-21

9.0.0 2025-04-16

8.6.0 2025-04-15

8.5.3 2025-04-09

8.5.2 2025-04-07

8.5.1 2025-04-02

8.5.0 2025-01-25

8.4.0 2025-01-11

8.3.0 2025-01-10

8.2.0-beta.1 2024-12-31

8.2.0 2025-01-03

8.1.0 2024-12-04

8.0.1 2024-08-22

8.0.0 2024-08-11

7.4.0 2024-07-10

7.3.0 2024-05-26

7.2.1 2024-05-26

7.2.0 2024-05-16

7.1.0 2023-09-05

7.0.1 2023-07-16

7.0.0 2023-07-15

6.2.0 2022-09-08

6.1.0 2022-07-08

6.0.0 2022-05-25

5.4.0 2022-05-25

5.3.1 2022-04-22

5.3.0 2022-04-22

5.2.0 2022-03-07

5.1.3 2022-03-06

5.1.2 2021-12-27

5.1.1 2021-12-16

5.1.0 2021-12-12

5.0.1 2021-12-11

5.0.0 2021-11-28

4.1.1 2021-02-01

4.1.0 2020-12-14

4.0.0 2019-12-18

3.1.0 2019-10-09

3.0.0 2019-05-17

2.2.8 2019-04-12

2.2.7 2019-02-20

2.2.6 2019-02-19

2.2.5 2019-02-19

2.2.4 2019-01-11

2.2.3 2018-11-30

2.2.2 2018-11-02

2.2.1 2018-10-27

2.2.0 2018-10-27

2.1.5 2018-09-04

2.1.4 2018-09-04

2.1.3 2018-09-03

2.1.2 2018-09-02

2.1.1 2018-09-02

2.1.0 2018-09-02

2.0.0 2018-05-18

1.3.0 2018-05-18

1.2.0 2018-02-03

1.1.3 2017-12-01

1.1.2 2017-12-01

1.1.1 2017-11-02

1.1.0 2017-11-02

1.0.0 2017-11-01

0.11.0 2017-10-31

0.10.2 2017-10-30

0.10.1 2017-10-30

0.10.0 2017-10-29

0.9.1 2017-10-26

0.8.3 2017-10-25

0.8.2 2017-10-25

0.8.1 2017-10-25

0.8.0 2017-10-25

0.7.0 2017-10-21

0.6.0 2017-10-20

0.4.0 2017-10-12

0.3.2 2017-10-12

0.3.1 2017-10-12

0.3.0 2017-10-12

0.2.2 2017-10-11

0.2.1 2017-10-11

0.2.0 2017-10-11

0.1.0 2017-09-28