array method

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js 内置 7种类型

基本类型: string number boolean null undefined symbol

引用类型: object

Array

es3/es5:

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//改变原数组
//push :向数组尾部添加数据 可添加多位
//自定义push
Array.prototype.push =function(){ }

//pop :剪切尾部一项数据
//unshift : 向数组前方添加数据
//revesre : 翻转数组

//splice : 第一个参数从第几位开始，第二个参数，截取几位，第三个参数覆盖截取的数据，返回截取的数据
/* 


sort :排序
一个函数为参数 ，同时 函数必须有两参数(a,b)
1. 函数返回值为正时 b在a前面
2. 为负数时 a在b前面
3. 0 时 不动
原理冒泡排序 */
 var obj = [{age:18,name:'1'},{age:38,name:'1'},{age:14,name:'1'},{age:28,name:'1'}], 
arr.sort(function(a,b){
    return a.age - b.age;//升序
})
//打乱有序的数组

arr.sort(function(a,b){
    return Math.random() - 0.6;
})



//不改变原数组需要变量接收
concat ： 拼接数组并返回 

join : 将数组每一位以传进的参数链接

slice : 第一个参数 开始截取为，第二个参数 截取到的位置

//将类数组转化为数组 
var arr=[].slice.call(arguments)

string methods

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var str ='123'
str.split('');

//camelize: 连字符转驼峰
const camelizeRE = /-(\w)/g
export const camelize = cached((str: string): string => {
  return str.replace(camelizeRE, ( _, c) => c ? c.toUpperCase() : '')
})

//变量的值转换为 string 类型并返回
export function toString (val: any): string {
  return val == null
    ? ''
    : typeof val === 'object'
      ? JSON.stringify(val, null, 2)
      : String(val)
}

interation method

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    const inventors = [
      { first: 'Albert', last: 'Einstein', year: 1879, passed: 1955 },
      { first: 'Isaac', last: 'Newton', year: 1643, passed: 1727 },
      { first: 'Galileo', last: 'Galilei', year: 1564, passed: 1642 },
      { first: 'Marie', last: 'Curie', year: 1867, passed: 1934 },
      { first: 'Johannes', last: 'Kepler', year: 1571, passed: 1630 },
      { first: 'Nicolaus', last: 'Copernicus', year: 1473, passed: 1543 },
      { first: 'Max', last: 'Planck', year: 1858, passed: 1947 },
      { first: 'Katherine', last: 'Blodgett', year: 1898, passed: 1979 },
      { first: 'Ada', last: 'Lovelace', year: 1815, passed: 1852 },
      { first: 'Sarah E.', last: 'Goode', year: 1855, passed: 1905 },
      { first: 'Lise', last: 'Meitner', year: 1878, passed: 1968 },
      { first: 'Hanna', last: 'Hammarström', year: 1829, passed: 1909 }
    ];


// Array.prototype.filter()
// 1. Filter the list of inventors for those who were born in the 1500's
let Filters= inventors.filter(el => el.year<1600 )
     console.table(Filters)
// Array.prototype.map()
// 2. Give us an array of the inventors' first and last names
let maps = inventors.map(el =>`${el.first} ${el.last}`)
     console.log(maps)
// Array.prototype.sort()
// 3. Sort the inventors by birthdate, oldest to youngest
     inventors.sort((a,b) => a.year-b.year)
     console.table(inventors)
// Array.prototype.reduce()
// 4. How many years did all the inventors live?
     let lives = inventors.reduce((first,second)=>(first+(second.passed - second.year)), 0)
     console.table(lives)
// 5. Sort the inventors by years lived
     inventors.sort((a,b) => -((a.passed-a.year)-(b.passed-b.year)))
     console.table(inventors)
      const people = [
      { name: 'Wes', year: 1988 },
      { name: 'Kait', year: 1986 },
      { name: 'Irv', year: 1970 },
      { name: 'Lux', year: 2015 }
    ];



const coms = [
     { text: 'Love this!', id: 523423 },
     { text: 'Super good', id: 823423 },
     { text: 'You are the best', id: 2039842 },
     { text: 'Ramen is my fav food ever', id: 123523 },
     { text: 'Nice Nice Nice!', id: 542328 }
];

// Some and Every Checks
// Array.prototype.some() // is at least one person 19 or older?
let isNineOld = people.some(el=> (new Date()).getFullYear() - el.year>=19)
// Array.prototype.every() // is everyone 19 or older?
let everyone=people.every(el=> (new Date()).getFullYear() - el.year>=19)
// Array.prototype.find()
// Find is like filter, but instead returns just the one you are looking for
// find the comment with the ID of 823423
let comment = coms.find(el=>el.id ===823423 )

// Array.prototype.findIndex()
// Find the comment with this ID
let i = coms.findIndex(el=>el.id ===823423 )

// delete the comment with the ID of 823423
let newcoms = [...coms.slice(0,i),coms.slice(i+1)]
coms.splice(i,1)

Label

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// 举一个比较典型的例子，看完后即明白 Label 的应用：（未添加 Label）
        var num = 0;
        for (var i = 0 ; i < 10 ; i++){
             for (var j = 0 ; j < 10 ; j++){
                  if( i == 5 && j == 5 ){
                        break;
                  }
             num++;
             }
        }
        alert(num); // 循环在 i 为5，j 为5的时候跳出 j循环，但会继续执行 i 循环，输出 95

// 对比使用了 Label 之后的程序：（添加 Label 后）
    var num = 0;
    outPoint:
    for (var i = 0 ; i < 10 ; i++){
         for (var j = 0 ; j < 10 ; j++){
              if( i == 5 && j == 5 ){
                    break outPoint;
              }
         num++;
         }
    }
    alert(num); // 循环在 i 为5，j 为5的时候跳出双循环，返回到outPoint层继续执行，输出 55
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