掌握 JavaScript 中的箭头函数

let functionname = (parameters) => {  // code to execute};

let greet = (name) => {  console.log("hello, " + name + "!");};greet("alice"); // output: hello, alice!

let square = x => x * x;console.log(square(5)); // output: 25

let add = (a, b) => a + b;console.log(add(3, 4)); // output: 7

let sayhello = () => console.log("hello!");sayhello(); // output: hello!

let multiply = (a, b) => a * b;console.log(multiply(2, 3)); // output: 6

function person() {  this.age = 0;  setinterval(() => {    this.age++;    console.log(this.age);  }, 1000);}let p = new person();// output: 1 2 3 4 ...

let count = 0;let increment = () => {  count++;  console.log(count);};increment(); // output: 1increment(); // output: 2

let numbers = [1, 2, 3, 4, 5];numbers.foreach(number => {  console.log(number * 2);});// output: 2 4 6 8 10

let getdayname = (day) => {  switch (day) {    case 1:      return "monday";    case 2:      return "tuesday";    case 3:      return "wednesday";    case 4:      return "thursday";    case 5:      return "friday";    case 6:      return "saturday";    case 7:      return "sunday";    default:      return "invalid day";  }};console.log(getdayname(3)); // output: wednesday

let processArray = (arr, callback) => {  for (let i = 0; i  {  console.log(number * 2);});// Output: 2 4 6 8 10