[游戏开发]项目常用到的代码片段

• 生成随机数

getRandom (x) {
     let val = '';
     if (x <= 10) {
       val = Math.random().toString().slice(2, x + 2)
     } else {
       let mul = Math.floor(x / 10)
       let surplur = x - 10 * mul
       for (let i = 0; i < mul; i++) {
         val += Math.random().toString().slice(2, 12)
       }
       surplur && (val = val + Math.random().toString().slice(2, surplur + 2))
     }
     return val
 }
getRandom(5)       //48668
getRandom(10)      //0562732990
getRandom(15)      //704678389507757
getRandom(20)      //33237146706223721325

• 声明和初始化数组

const array = Array(5).fill('')
array   //['','','','','']

const matrix = Array(5).fill(0).map(()=>Array(5).fill(0))
matrix  
//[Array(5),Array(5),Array(5),Array(5),Array(5)]
//0:[0,0,0,0,0]
//1:[0,0,0,0,0]
//2:[0,0,0,0,0]
//3:[0,0,0,0,0]
//4:[0,0,0,0,0]

• 找出总和、最小值、最大值

const array = [5,4,7,8,9,2]
array.reduce((a,b)=>a+b)        //35
array.reduce((a,b)=>a>b?a:b)    //9
array.reduce((a,b)=>a<b?a:b)    //2

• 对字符串、数字或对象数组进行排序

--排序字符串数组
const stringArr = ['Joe','Kapil','Steve','Musk']
stringArr.sort()   //["Joe", "Kapil", "Musk", "Steve"]
stringArr.reverse()  //["Steve", "Musk", "Kapil", "Joe"]

--排序数字数组
const array = [40,100,1,5,25,10]
array.sort((a,b)=>a-b)    //[1, 5, 10, 25, 40, 100]
array.sort((a,b)=>b-a)    //[100, 40, 25, 10, 5, 1]

--对象数组排序
const objectArr = [
	{first_name:'Lazslo',last_name:'Jamf'},
	{first_name:'Pig',last_name:'Bodine'},
	{first_name:'Pirate',last_name:'Prentice'},
]
objectArr
//[{...},{...},{...}]
0:{first_name:'Pig',last_name:'Bodine'}
1:{first_name:'Lazslo',last_name:'Jamf'}
2:{first_name:'Pirate',last_name:'Prentice'}

• 从数组中过滤出虚假值

const array = [3,0,6,7,'',false]
array.filter(Boolean)   //[3,6,7]

• 使用逻辑运算符代替if…else嵌套

function doSomething(arg1){
	arg1 = arg1 || 10
	return arg1
}
let foo = 10
foo === 10 && doSomething()     //10
foo === 5 || doSomething()      //10
foo === 10 || doSomething()     //true

• 三元运算符

function Fever(temp){
	return temp > 97 ? 'Visit Doctor!' : temp < 97 ? 'Go Out and Play!!' : temp === 97 ? 'Take  Some Rest!'
}
Fever(97)   //'Take some Rest!'
Fever(100)  //'Visit Doctor!'

• 创建计数器对象或映射

let string = 'kkkapiliekty'
const table = {}
for(let char of string){
	table[char] = table[char] + 1 || 1 
}
table     //{a: 1,e: 1,i: 2,k: 4,l: 1,p: 1,t: 1,y: 1}

• 使用解构简单交换两值

let a = 5
let b = 8
[a,b] = [b,a]
[a,b]   //[8,5]