ES6ios
1. var let constes6
let,const具備塊級做用域,不具備變量提高axios
const 用於不能被從新賦值的變量數組
2. 箭頭函數異步
咱們常常要給回調函數給一個父級的thisasync
經常使用辦法就是 var self = this 定義一個變量接住他函數
使用 箭頭函數,this 將不會受到影響,能夠直接用this調用父級的thisfetch
3. 字符串this
includes:rest
const string = 'food';
const substring = 'foo';
console.log(string.includes(substring));
返回的是布爾值。
string.repeat(str,count)
若是 string.length < count 即插入str到count == string.length爲止
4. 模板字符串
const name = 'Tiger';
const age = 13;
console.log(`My cat is named ${name} and is ${age} years old.`);
5.解構
結構數組:
let [a, b, c, d] = [1, 2, 3, 4];
console.log(a);
console.log(b);
結構對象:
var luke = { occupation: 'jedi', father: 'anakin' };
var occupation = luke.occupation;
var father = luke.father;
-------------------------------------------------------------
let luke = { occupation: 'jedi', father: 'anakin' };
let {occupation, father} = luke;
console.log(occupation);
console.log(father);
6.模塊
暴露對象:
function sumThree(a, b, c) {
return a + b + c;
}
export { sumThree };
引入:
import { sumThree } from 'math/addition';
7.參數
es6支持設置默認值:
function addTwoNumbers(x=0, y=0) {
return x + y;
}
8.rest參數
處理不定數目參數:
function logArguments(...args) {
for (let arg of args) {
console.log(arg);
}
}
9.展開操做
能夠展現數組:
Math.max(...[-1, 100, 9001, -32]);
let cities = ['San Francisco', 'Los Angeles'];
let places = ['Miami', ...cities, 'Chicago']; // ['Miami', 'San Francisco', 'Los Angeles', 'Chicago']
10.類
創造類:
class Person {
constructor(name, age, gender) {
this.name = name;
this.age = age;
this.gender = gender;
}
incrementAge() {
this.age += 1;
}
}
11.Maps
能夠理解成鍵值對
let map = new Map();
map.set('name', 'david');
map.get('name');
map.has('name');
12.Promises
遠離回調地獄,能夠轉換成垂直代碼
func1(value1)
.then(func2)
.then(func3)
.then(func4)
.then(func5, value5 => {
});
13.Generators
用同步的代碼風格來寫異步代碼
function* genFunc() {
// (A)
console.log('First');
yield; //(B)
console.log('Second'); //(C)
}
ES7
1. includes
代碼:
let array = ['1','2','3']
if(array.includes('2')){
console.log('有')
}
2. 指數操做符
2**3 == 8
ES8
1. object.entries()
代碼:
let obj = {a: 1, b: 2, c: 3};
Object.entries(obj).forEach(([key, value]) =>{
console.log(key + ": " + value); // 輸出a: 1, b: 2, c: 3
})
2.Async Await
異步看起來和同步寫法同樣
代碼:
async fetchData(query) =>{
try {
const response = await axios.get(`/q?query=${query}`);
const data = response.data;
return data;
}
catch (error) {
console.log(error)
}
}
fetchData(query).then(data => {
this.props.processfetchedData(data)
})