ES6
1.const 和 let
2.箭头函数和默认值 以及 args
3.扩展运算符
4.对象属性冻结
5.解构赋值...
1.对象的结构赋值
// 基础
const HIGH_TEMPERATURES = {
yesterday: 75,
today: 77,
tomorrow: 80,
};
const { today, tomorrow } = HIGH_TEMPERATURES;
// 结构赋值 在提取值时分配新的变量名称 highToday = 77
const { today: highToday, tomorrow: highTomorrow } = HIGH_TEMPERATURES;
// 多层解构
const LOCAL_FORECAST = {
yesterday: { low: 61, high: 75 },
today: { low: 64, high: 77 },
tomorrow: { low: 68, high: 80 },
};
const {
today: { low: lowToday, high: highToday },
} = LOCAL_FORECAST;
2.数组的结构赋值
// 基础
const [a, b] = [1, 2, 3, 4, 5, 6];
console.log(a, b); // 1, 2
// 逗号当作索引
const [a, b, , , c] = [1, 2, 3, 4, 5, 6];
console.log(a, b, c); // 1, 2, 5
// 应用 快速交换两个参数数值
let a = 8,
b = 6;
[b, a] = [a, b];
//结合扩展运算符
const [a, b, ...arr] = [1, 2, 3, 4, 5, 7];
console.log(a, b); // 1, 2
console.log(arr); // [3, 4, 5, 7]
// 变成slice 方法
const source = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
function removeFirstTwo(list) {
const [, , ...arr] = list;
console.log(arr, list);
return arr;
}
const arr = removeFirstTwo(source);
3.传参时候对参数进行解构
const stats = {
max: 56.78,
standard_deviation: 4.34,
median: 34.54,
mode: 23.87,
min: -0.75,
average: 35.85
};
const half = ({max,min}) => (max+min) / 2.0;
6.模板字符串
7.对象速写
1.对象的键值上
const getMousePosition = (x, y) => ({
x: x,
y: y,
});
const getMousePosition = (x, y) => ({ x, y });
2.对象存储的方法上
// OLD
const person = {
name: "Taylor",
sayHello: function () {
return `Hello! My name is ${this.name}.`;
},
};
// NEW
const person = {
name: "Taylor",
sayHello() {
return `Hello! My name is ${this.name}.`;
},
};
8.类组件 替换构造函数
1.构造函数和类
// 构造函数
var SpaceShuttle = function (targetPlanet) {
this.targetPlanet = targetPlanet;
};
var zeus = new SpaceShuttle("Jupiter");
// 类 和python一样
var SpaceShuttle = function (targetPlanet) {
this.targetPlanet = targetPlanet;
};
var zeus = new SpaceShuttle("Jupiter");
2.使用 setter 和 getter 【Java】
// Only change code below this line
class Thermostat {
constructor(temperature) {
this._temperature = (5 / 9) * (temperature - 32);
}
get temperature() {
return this._temperature;
}
set temperature(temperature) {
this._temperature = temperature;
}
}
// Only change code above this line
const thermos = new Thermostat(76); // Setting in Fahrenheit scale
let temp = thermos.temperature; // 24.44 in Celsius
thermos.temperature = 26;
temp = thermos.temperature; // 26 in Celsius
console.log(temp);
9.使用 script 的 type = module 模块化
1.export 和 import
// 导入全部内容
import * as stringFunctions from "./string_functions.js";
// Only change code above this line
stringFunctions.uppercaseString("hello");
stringFunctions.lowercaseString("WORLD!");
2.默认导出
// export default与var，let或const 不能一起使用
// named function
export default function add(x, y) {
return x + y;
}
// anonymous function
export default function(x, y) {
return x + y;
}