Ifx?

ifx is a JavaScript module that provides "if-expression" to return a value. It can be alternative to ternary operator.

Motivation

Use of ternary operators to express stateless values and functions tends to result in significantly diminished readability when applied to complicated nesting conditions or multiple conditions.
I wanted to use conditional branches built on JavaScript which return values in the same manner as the if-expression in Scala to ensure readability in such situation.

Usage

install

npm install ifx

import

const If = require('ifx');

ES6 syntax (recommend)

// stateless and readable to use ES6 arrow function
const x = If(false)(() => 1).ElseIf(true)(() => 2).Else(() => 3);
console.log(x);

formatted

// can be return value
const fn = value =>
  If(value instanceof Array)(() => value.map(x =>
    If(typeof x === 'number')(() => x * 5).Get()))
  .ElseIf(value instanceof Object)(() => Object.keys(value))
  .Else(() => [])
  .filter(x => x !== null);

console.log(fn([1,2,null,3,4,5]));    // [ 5, 10, 15, 20, 25 ]
console.log(fn({a: 1, b: 2, c: 3}));  // [ 'a', 'b', 'c' ]
console.log(fn(2));                   // []

ES5 syntax

var If = require('ifx');

var x = If(false)(function () { return 1 })
    .ElseIf(true)(function () { return 2 })
    .Else(function () { return 3 });

console.log(x);  // 2

API

If = condition -> expected function -> object

If is a curried function.
returned-object has methods Else/ElseIF/Get

// every type can be returning value
console.log(If(true)(() => true).Get());  // true
console.log(If(true)(() => 'a').Get());   // a
console.log(If(true)(() => null).Get());  // null
console.log(If(true)(() => {}).Get());      // undefined
console.log(If(true)(() => [1]).Get());   // [ 1 ]
console.log(If(true)(() => ({})).Get());    // {}

// returned function apply to function only
try {If(true)(1).Get()} catch(e) {console.log(e)}   // [Error: If() con be applied to a function only]

.Get = () -> value

if you don't use Else, Get gets rerutning a value.

// If(true)
console.log(If(true)(() => 1).Get());   // 1

// If(false)
console.log(If(false)(() => 1).Get());  // null

.Else = function -> value`

When you use Else, Get is unnecessary.

// If + Else
console.log(If(false)(() => 1).Else(() => 2));  // 2

.ElseIf = condition -> expected function -> object

Chain ElseIf, if you need conditions more than once.

// If + ElseIf + Get
console.log(If(false)(() => 1).ElseIf(true)(() => 2).Get());                        // 2
console.log(If(false)(() => 1).ElseIf(false)(() => 2).ElseIf(true)(() => 3).Get()); // 3

// If + ElseIf + Else
console.log(If(false)(() => 1).ElseIf(false)(() => 2).ElseIf(false)(() => 3).Else(() => 4));  // 4

// need condition
try {If(true)(() => 1).ElseIf()(() => 2).Get()} catch(e) {console.log(e)}  // [Error: ElseIf connot be applied to an empty value]

TypeScript Import

import * as If from 'ifx';

about specs

It returns first matched value when conditions match more than once.

console.log(If(true)(() => 1).ElseIf(false)(() => 2).ElseIf(false)(() => 3).Else(() => 4)); // 1
console.log(If(false)(() => 1).ElseIf(false)(() => 2).ElseIf(true)(() => 3).Get());         // 3

It returns null when all conditions don't match.

console.log(If(false)(() => 1).ElseIf(false)(() => 2).Get());                        // null
console.log(If(false)(() => 1).ElseIf(false)(() => 2).ElseIf(false)(() => 3).Get()); // null

Author

jshosomichi

License

under the MIT license.

jshosomichi/ifx