ES6(1)

目錄

 

2.實時刷新

3.查找字符串

4.複製字符串

5.數字的操作

6.數組

---

2.實時刷新

---

1.項目初始化

npm init

2.安裝

cnpm i -g live-server

3.啓動

live-server

3.查找字符串

---

indexOf()

let blog = `向暖lalallzenm hdjhd糖糖shd`
document.write(blog.indexOf('糖糖')==-1)//false

includes()

let blog = `向暖lalallzenm hdjhd糖糖shd`
document.write(blog.includes('糖糖'))//true

startsWith()

let blog = `向暖lalallzenm hdjhd糖糖`
document.write(blog.startsWith('糖糖'))//false

endsWith()

let blog = `向暖lalallzenm hdjhd糖糖`
document.write(blog.endsWith('糖糖'))//true

4.複製字符串

---

let blog = `糖糖`
document.write(blog.repeat(10))

5.數字的操作

---

//二進制聲明 Binary
let binary = 0B010101;
document.write(binary)//21

//八進制聲明 Octal
let octal = 0o666;
document.write(octal)//438

//判斷是否是數字
let a =20 ;
document.write(Number.isFinite(a))//true
document.write(Number.isFinite(NaN))//false
document.write(Number.isFinite(undefined))//false

//isNaN 和 Number.isNaN
//isNaN：只是判斷傳入的參數是否能轉換成數字，並不是嚴格的判斷是否等於NaN,如果成功返回false，如果失敗返回true
document.write(isNaN('true'))//true
//判斷傳入的參數是否嚴格的等於NaN(也就是 ===),不存在類型轉換的行爲
document.write(Number.isNaN(1))//fasle
document.write(Number.isNaN(1/'測試'))//true


//判斷是否爲整數
let a = 999.1;
document.write(Number.isInteger(a))//false

6.數組

---

//json的數組格式
let json = {
    "0":"糖糖",
    "1":18,
    "2":"女",
    length:3
}
let arr  = Array.from(json);
console.log(arr);//["糖糖", 18, "女"]


let arr2 = Array.of(2,3,5);
console.log(arr2);//[2,3,5]


//find()實例方法
//value:當前查找的值
//index:索引
//arr:原型
let arr  = [2,3,4,5,6,7];
console.log(arr.find(function(value,index,arr){
    return value > 5//查找第一個並返回
}))

for ... of

let arr =['age','vivi','bibi','yoyo',18];
for(let item of arr.entries()){
    console.log(item)
}

function add(a,b=1){
    if(a==0){
        throw new Error('A is Error')
    }
    return a+b
}
console.log(add.length)//1 只顯示必須傳遞的


//Es6
var add=(a,b=1)=>a+b;
console.log(add(2));//3