Functional Programming for EcmaScript(Javascript)
Documentation: see
docs/OVERVIEW.mdfor the module map, non-obvious behaviors, and a scenarios cookbook, anddocs/API.mdfor the full export reference. The README below only covers a small subset of the API.
Originally I would like to have some features of Optional & Rx-like & PubSub functions;
however somehow that's too heavy if including them at the same time.
Thus the implementation just includes the core functions, and more clear to use.
- purify (Inspiration from parts of Maybe implementations for Fantasy-Land Specs)
node >= 8.3.0
- Installation:
npm i fpesbundled files for web/browser usages:
In the browser bundle, the global name is fpEs (see webpack library setting). In Node/npm, install and import the package as fpes (all lowercase).
- You can include the entire library:
import fpEs from 'fpes';- There are 5 modules in this library, you can include them individually:
- Facades:
- maybe
- monadio
- publisher
- FP functions:
- fp
- pattern
- Facades:
Just include things you need:
import {Maybe} from "fpes";
// or this one:
/*
import Maybe from "fpes/maybe";
*/
var m = Maybe.just(1); // It worksor
import {
compose, curry,
} from "fpes";or
import {
compose, curry,
} from "fpes/fp";Example:
import {
compose, curry,
} from "fpes/fp";
// compose
console.log(compose((x)=>x-8, (x)=>x+10, (x)=>x*10)(4)) // 42
console.log(compose((x)=>x+2, (x,y)=>x*y)(4,10)) // 42
// curry
console.log(curry((x, y, z) => x + y + z)(1,2,3)) // 6
console.log(curry((x, y, z) => x + y + z)(1)(2,3)) // 6
console.log(curry((x, y, z) => x + y + z)(1,2)(3)) // 6
console.log(curry((x, y, z) => x + y + z)(1)(2)(3)) // 6Example:
import {
either,
inCaseOfObject, inCaseOfEqual, inCaseOfClass, otherwise,
SumType, ProductType, CompType,
TypeNumber,
TypeString,
TypeNaN,
TypeObject,
TypeArray,
TypeNull,
TypeEqualTo,
TypeClassOf,
TypeRegexMatches,
} from "fpes/pattern";
// PatternMatching
console.log(either({}, inCaseOfObject((x)=>JSON.stringify(x)), otherwise((x)=>false))); // "{}"
console.log(either([], inCaseOfObject((x)=>JSON.stringify(x)), otherwise((x)=>false))); // false
console.log(either(null, inCaseOfObject((x)=>JSON.stringify(x)), otherwise((x)=>false))); // false
console.log(either(undefined, inCaseOfObject((x)=>JSON.stringify(x)), otherwise((x)=>false))); // false
console.log(either("", inCaseOfObject((x)=>JSON.stringify(x)), otherwise((x)=>false))); // false
// otherwise
var err = undefined;
err = undefined;
either(1, inCaseOfEqual(1, (x)=>x+1)).should.equal(2);
(err === undefined).should.equal(true);
err = undefined;
try {
either(1, inCaseOfEqual(2, (x)=>x+1));
} catch (e) {
err = e;
}
(err === undefined).should.equal(false);
err = undefined;
try {
either(1, inCaseOfEqual(2, (x)=>x+1), otherwise((x)=>x+2)).should.equal(3);
} catch (e) {
err = e;
console.log(e);
}
(err === undefined).should.equal(true);
// SumType
var s;
s = new SumType(new ProductType(TypeString, TypeNumber), new ProductType(TypeRegexMatches('c+')));
console.log(s.apply("1", "2asdf") === undefined); // true
console.log(s.apply("1", 2) === undefined); // false
console.log(s.apply("1") === undefined); // true
console.log(s.apply("ccc") === undefined); // falseExample:
import Maybe from "fpes/maybe";
var m;
// map (sync)
m = Maybe.just(1).map((x)=>x+2).map((x)=>x+3);
console.log(m.unwrap()); // 6
// isPresent/isNull
m = Maybe.just(1);
console.log(m.isPresent()); // true
console.log(m.isNull()); // false
m = Maybe.just(null);
console.log(m.isPresent()); // false
console.log(m.isNull()); // true
m = Maybe.just(undefined);
console.log(m.isPresent()); // false
console.log(m.isNull()); // true
// Or
m = Maybe.just(1);
console.log(m.or(3).unwrap()); // 1
console.log(m.or(4).unwrap()); // 1
m = Maybe.just(null);
console.log(m.or(3).unwrap()); // 3
console.log(m.or(4).unwrap()); // 4
m = Maybe.just(undefined);
console.log(m.or(3).unwrap()); // 3
console.log(m.or(4).unwrap()); // 4
// letDo
m = Maybe.just(1);
v = 0;
m.letDo(function () {
v = 1;
});
console.log(v); // 1
m = Maybe.just(null);
v = 0;
m.letDo(function () {
v = 1;
});
console.log(v); // 0
m = Maybe.just(undefined);
v = 0;
m.letDo(function () {
v = 1;
});
console.log(v); // 0
// letDo & orDo
m = Maybe.just(0);
v = m.letDo(function (p) {
return p + 2
}).orDo(function () {
return 3
}).unwrap();
console.log(v); // 2
m = Maybe.just(undefined);
v = m.letDo(function (p) {
return p + 2
}).orDo(function () {
return 3
}).unwrap();
console.log(v); // 3Example:
import Maybe from "fpes/maybe";
import MonadIO from "fpes/monadio";
var {promiseof, doM} = MonadIO;
var p = undefined;
var m = MonadIO.just(0);
var v = 0;
// sync
m = MonadIO.just(0);
v = 0;
m
.map((val)=>val+1)
.map((val)=>val+2)
.flatMap((val)=>MonadIO.just(val+1).map((val)=>val+1).map((val)=>val+1))
.subscribe((val)=>v=val);
console.log(v); // 6
// async
m = MonadIO.just(0);
v = 0;
p = m
.map((val)=>val+1)
.map((val)=>val+2)
.map((val)=>val+3)
.subscribe((val)=>v=val, true); // Async: true
console.log(v); // 0
p.then(function () {
console.log(v); // 6
});
// DoNotation
v = 0;
p = doM(function *() {
var value = yield promiseof(5);
var value2 = yield promiseof(11);
var value3 = yield Maybe.just(3);
var value4 = yield MonadIO.just(3);
return value + value2 + value3 + value4;
});
p.then((x)=>console.log(x)); // 22Example:
import Publisher from "fpes/publisher";
var p = new Publisher();
var v = 0;
// sync
p = new Publisher();
v = 0;
p.subscribe((i)=>v=i);
p.publish(1);
console.log(v); // 1
// async
p = new Publisher();
v = 0;
p.subscribe((i)=>v=i);
p.publish(1, true); // Async: true
console.log(v); // 0
setTimeout(()=>{
console.log(v); // 1
},100);
// map
p = new Publisher();
v = 0;
p.map((x)=>x+2).map((x)=>x+3).subscribe((i)=>v=i);
p.publish(1, true);
console.log(v); // 0
setTimeout(()=>{
console.log(v); // 6
},100);
// unsubscribe
p = new Publisher();
v = 0;
var callback = (i)=>v=i;
p.subscribe(callback);
p.publish(1);
console.log(v); // 1
v = 0;
p.unsubscribe(callback);
p.publish(1);
console.log(v); // 0- Node
^22.18.0 || >=24.11.0(required by Babel 8 dev toolchain) - Consumer runtime:
>= 8.3.0(seeenginesinpackage.json)
npm run release:check— run tests, run thepreparebuild throughnpm pack, and verify tarball contents- Inspect the
npm pack --dry-run --jsonfile list (no test/config leak; docs links included) git tag -a v<version> -m "Release <version>"— create version tag at the final release commitnpm login— authenticate to npmnpm publish(add--otp=<code>if 2FA enabled)git push origin master— push the release commit explicitlygit push origin v<version>— push only the release tag explicitly- Verify unpkg:
https://unpkg.com/fpes@<version>/dist/bundle.min.js