@andrwj/fp

FPJS

A Functional tool set for my own learning FP style. Implemented by referring many other's source.

Introduced the beginning of this repository in Medium post

Installation

npm install @andrwj/fp

Either

static methods

• Either.of(value, f)
• Either.fromNullable(value)
• Either.filter(f, condition_f=truth) - condition_f is optional
• Either.right(value)
• Either.left(value)
• Either.done(value)
• Either.doneIf(f, value)
• Either.throw(value) - this throws Right(value) not Error instnace !!! and then only .catch() handle the passed Right
• Either.throwIf(f, value)
• Either.try(f)

instance methods for Right

• .inspect(f)
• .try(f)
• .throw()
• .tap(f=console.log)
• .take(f)
• .map(f)
• .chain(f)
• .filter(f)
• .fold(_right, _left)
• .done()
• .doneIf(f)
• .throwIf(f, value)
• .apply( instance_of_Either )

instance methods for Left

• .inspect(f)
• .tap(f=console.log)
• .take(f)
• .fold(_right, _left)

NOTE

• All methods work for Right only.
• Only Right can .throw() or .done()
• Basically Left will skip most methods except inspect, tap, take, fold
• throw() does not throw Error. It is deliver of Right to .catch().
• If you throw(), execution flow goes until find .catch()
• If you done(), execution flow goes until find .fold() or .take()
• If there is no exception in try(f), return value will be of Right. If Exception occurs, then the return value will be of Left.
• If you do not want to get Unhandled Promise Rejection Error in .try(f), you HAVE TO deal with its logic of f yourself. The unhandled error is not because of .try() but because of your misunderstanding of Promise chain.

Fromise (Experimental; Promimse + Either)

• Fromise.resolve (expr)
• Fromise.reject (expr)
• Fromise.isPromise (value)
• .pipe (...funcs)
• .if (f_condition, if_true, if_false)
• .tap (f)
• .either (f)
• .map (f)
• .fold (f, g)
• .chain (f)

High Order Functions (Not fully documented yet)

• run(v, f1, f2, f3, ... ) : value
• pipe(f1, f2, f3, ...) : function

Utilities (Not fully documented yet)

• isFunction (v) - return true if v is function
• isFalsy (v) - true if v is one of undefined, NaN, null
• isFalse (v) - true if v is one of undefined, NaN, null, 0, ""
• identity (v) - returns v, always.

Logic Gates

• import {NOT, OR, AND, NAND, NOR, XOR, XNOR, chart_dump} from FPJS;

Test Source Codes with RunJS

// use loader.js for local developing
// for example:
import {Either} from '/Users/andrwj/Develops/FPJS/FPJS/loader';

Changes

v0.2.4 Published compiled source by Babel7

v0.2.0 break changes to version of 0.1.*

• changed arguments order and way: Either.of(f, value) ➡ Either.of(value, f) - if f is not given, it just returns Right(value). Otherwise, it returns Right(value) or Left(value) depends on the boolean result of f(value)
• changed arguments: .catch(f, condition_f) ➡ .catch(f) - if f is not given, it returns the instance of thrown from .throw(). Otherwise it returns .map(f)
• added: .of(value, f) - same as Either.of(value, f)
• added: isNotFalsy(v) : boolean