JavaScript中的函式與命令模式，Java也有參考價值

const hour = 14
let greeting

if (hour < 18) {
greeting = 'Good day';
} else {
greeting = 'Good evening';
}

const isDay = hour => hour < 18
const getGreeting = hour => isDay(hour) ? 'Good Day' : 'Good Evening'
const greeting = getGreeting (hour)

let name = 'joel'

if (name != null) {
name = name.toUpperCase()
}

函式正規化：
isNotnull和toUpperCase市可重用的函式：

import when from 'mojiscript/logic/when'

const isNotNull = obj => obj != null
const toUpperCase = when (isNotNull) (string => string.toUpperCase ())

const name = 'joel'
const upperName = toUpperCase (name)


[b]陣列相加[/b]

const values = [1, 2, 3]

let sum = 0
for (const x of values) {
sum = sum + x
}

函式正規化：
不將sum變成可變變數：

const values = [1, 2, 3]

const add = (x, y) => x + y
const sum = values.reduce(add)

[b]for/if[/b]
命令正規化：

const values = [1, 2, 3, 4, 5]

let evens = []
for (const x of values) {
if (x % 2 === 0) {
evens.push(x)
}
}

函式正規化：
不要將evens成為可變：

import filter from 'mojiscript/list/filter'

const values = [1, 2, 3, 4, 5]

const isEven = num => num % 2 === 0
const evens = filter (isEven) (values)


[b]提前中斷迴圈[/b]
命令正規化：

const values = [1, 2, 3]
let sum = 0
for (const x of values) {
if (x > 3) break
sum = sum + x 
}

函式正規化：
使用reduceWhile，類似reduce，能接受一個

import reduceWhile from 'mojiscript/list/reduceWhile'

const add = x => y => x + y
const lte3 = num => num <= 3

const sum = reduceWhile (() => lte3) (add) (0) (values)

命令正規化：

const fn = temp => {
if (temp === 0) return 'water freezes at 0°C'
else if (temp === 100) return 'water boils at 100°C'
else return `nothing special happens at ${temp}°C`
}

fn(0) //=> 'water freezes at 0°C'
fn(50) //=> 'nothing special happens at 50°C'
fn(100) //=> 'water boils at 100°C'

函式正規化：

import cond from 'mojiscript/logic/cond'
import $ from 'mojiscript/string/template'

const fn = cond([
[0, 'water freezes at 0°C'],
[100, 'water boils at 100°C'],
[() => true, $`nothing special happens at ${0}°C`]
])

fn(0) //=> 'water freezes at 0°C'
fn(50) //=> 'nothing special happens at 50°C'
fn(100) //=> 'water boils at 100°C'

[b]類
[/b]命令正規化：

class Cat {
constructor() {
this.sound = 'Meow'
}

talk() {
return this.sound
}
}

const cat = new Cat()
const talk = cat.talk

cat.talk() //=> 'Meow'
talk() //=> Error: Cannot read property 'sound' of undefined

函式正規化：

const cat = {
sound: 'Meow'
}

const dog = {
sound: 'Woof'
}

const talk = animal => animal.sound

talk (cat) //=> 'Meow'
talk (dog) //=> 'Woof'

檢查空NULL

命令正規化：

const toUpper = string => {
if (string != null) {
return string.toUpperCase()
}
}

函式正規化：

Maybe

Maybe

string