FxJS is a functional Javascript library based on Iterable / Iterator, Generator, and Promise in ECMAScript 6.
<script src="https://unpkg.com/fxjs/dist/fx.js"></script>
<script src="https://unpkg.com/fxjs/dist/fx.es5.js"></script>
<script>
const { L, C } = window._;
_.go(
[1, 2, 3],
L.map(a => a * a),
L.map(_.delay(300)),
C.takeAll,
_.reduce(_.add),
console.log
);
// '14' output after about 300 ms
</script>
fx.js script file, _ is used as a global variable.FxJS is a Dual Module Package that supports both CommonJS and ES6 Module.
Among the two module types of the fxjs package, commonjs support node.js v6 or higher, and ESM is available from node.js v12 or higher.
npm install fxjs
CommonJS (>= node v6)
const FxJS = require("fxjs");
const _ = require("fxjs/Strict");
const L = require("fxjs/Lazy");
const C = require("fxjs/Concurrency");
// The module object that exported as default has all the functions in fxjs, including Lazy and Concurrency.
const { reduce, mapL, takeAllC } = FxJS;
// You can also import the functions individually.
const rangeL = require("fxjs/Lazy/rangeL");
_.go(
rangeL(1, 4),
L.map(a => a * a),
L.map(_.delay(300)),
C.takeAll,
_.reduce(_.add),
console.log
);
ES6 Module (>= node v12)
import { add, delay, go, reduce, rangeL } from "fxjs";
import * as L from "fxjs/Lazy";
import * as C from "fxjs/Concurrency";
go(
rangeL(1, 4),
L.map(a => a * a),
L.map(delay(300)),
C.takeAll,
reduce(add),
console.log
);
FxJS adopted the Isolate state approach in two ways to support the Dual Module Package, which was introduced in the official Node.js document. Therefore, when using both CommonJS and ES modules, care must be taken to compare the equivalence of modules or function objects as shown below. For more information, see Node.js Document.
import { createRequire } from "module";
import * as fxjs_mjs from "fxjs";
import go_mjs from "fxjs/Strict/go.js";
const require = createRequire(import.meta.url);
const fxjs_cjs = require('fxjs');
const go_cjs = require('fxjs/Strict/go');
console.log(fxjs_mjs === fxjs_cjs); // false
console.log(go_mjs === go_cjs); // false
console.log(fxjs_cjs.go === go_cjs); // true
console.log(fxjs_mjs.go === go_mjs); // true
You can evaluate the iterator as a function of FxJS.
function* fibonacci() {
let a = 0,
b = 1;
while (true) {
yield a;
[a, b] = [b, a + b];
}
}
const f = pipe(
fibonacci,
L.filter((n) => n % 2 == 0),
L.takeWhile((n) => n < 10)
);
const iterator = f();
console.log(iterator.next()); // { value: 0, done: false }
console.log(iterator.next()); // { value: 2, done: false }
console.log(iterator.next()); // { value: 8, done: false }
console.log(iterator.next()); // { value: undefined, done: true }
reduce((a, b) => a + b, f());
// 10
Any value can be used with FxJS if it has a [Symbol.iterator]() method.
const res = go(
[1, 2, 3, 4, 5],
filter((a) => a % 2),
reduce(add)
);
log(res); // 9
You can do 'lazy evaluation' as a function of the L namespace.
const res = go(
L.range(Infinity),
L.filter((a) => a % 2),
L.take(3),
reduce(add)
);
log(res); // 9
Functional reactive programming style.
go(
L.range(Infinity),
L.map(delay(1000)),
L.map((a) => a + 10),
L.take(3),
each(log)
);
// After 1 second 10
// After 2 seconds 11
// After 3 seconds 12
Asynchronous control is easy.
// L.interval = time => L.map(delay(time), L.range(Infinity));
await go(
L.interval(1000),
L.map((a) => a + 30),
L.takeUntil((a) => a == 33),
each(log)
);
// After 1 second 30
// After 2 seconds 31
// After 3 seconds 32
// After 4 seconds 33
const res = await go(
L.interval(1000),
L.map((a) => a + 20),
L.takeWhile((a) => a < 23),
L.map(tap(log)),
reduce(add)
);
// After 5 seconds 20
// After 6 seconds 21
// After 7 seconds 22
log(res);
// 63
C functions can be evaluated concurrency.
await map(getPage, range(1, 5));
// After 4 seconds
// [page1, page2, page3, page4]
const pages = await C.map(getPage, range(1, 5));
// After 1 second
// [page1, page2, page3, page4]
Like Clojure Reducers, you can handle concurrency.
go(
range(1, 5),
map(getPage),
filter((page) => page.line > 50),
map(getWords),
flat,
countBy(identity),
log
);
// After 4 seconds
// { html: 78, css: 36, is: 192 ... }
go(
L.range(1, 5),
L.map(getPage),
L.filter((page) => page.line > 50),
L.map(getWords),
C.takeAll, // All requests same time.
flat,
countBy(identity),
log
);
// After 1 second
// { html: 78, css: 36, is: 192 ... }
go(
L.range(1, 5),
L.map(getPage),
L.filter((page) => page.line > 50),
L.map(getWords),
C.takeAll(2), // 2 requests same time.
flat,
countBy(identity),
log
);
// After 2 second
// { html: 78, css: 36, is: 192 ... }
You can use JavaScript standard error handling.
const b = go(
0,
(a) => a + 1,
(a) => a + 10,
(a) => a + 100
);
console.log(b);
// 111
try {
const b = go(
0,
(a) => {
throw { hi: "ho" };
},
(a) => a + 10,
(a) => a + 100
);
console.log(b);
} catch (c) {
console.log(c);
}
// { hi: 'ho' }
You can use async/await and try/catch to handle asynchronous error handling.
const b = await go(
0,
(a) => Promise.resolve(a + 1),
(a) => a + 10,
(a) => a + 100
);
console.log(b);
// 111
try {
const b = await go(
0,
(a) => Promise.resolve(a + 1),
(a) => Promise.reject({ hi: "ho" }),
(a) => a + 100
);
console.log(b);
} catch (c) {
console.log(c);
}
// { hi: 'ho' }
The above libraries are based on FxJS. FxSQL and FxDOM are libraries that can handle SQL and DOM through functional APIs,respectively.
FAQs
Functional Extensions for modern Javascript
We found that fxjs-test demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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