Node.js箭头函数

(parameters) => {
  statements;
};

function (parameters) {
  statements;
}

// 匿名函数赋值
const squareFun1 = function (x) {
  return x * x;
};

// 箭头函数省略function关键字
const squareFun2 = (x) => {
  return x * x;
};

// 如果函数体中只有一句statement，可以省略大括号
const squareFun3 = (x) => x * x;

console.log(squareFun1(2)); // output: 4
console.log(squareFun2(2)); // output: 4
console.log(squareFun3(2)); // output: 4

const person = {
  name: "shiming",
  getName1: function () {
    return this.name;
  },
  getName2() {
    return this.name;
  },
  getName3: () => {
    return this.name;
  },
};

console.log(person.getName1()); // output: shiming
console.log(person.getName2()); // output: shiming
console.log(person.getName3()); // output: undefined

const students = {
  students: [
    { name: "alice", gender: "female" },
    { name: "bob", gender: "male" },
    { name: "frank", gender: "male" },
    { name: "lily", gender: "female" },
  ],
  getFemaleStudents1() {
    const femaleStudents = this.students.filter(function (student) {
      return student.gender === "female";
    });
    return femaleStudents;
  },
  // 优化一：减少一个const声明;用一个箭头函数替代了filter中的匿名函数
  getFemaleStudents2() {
    return this.students.filter((student) => {
      return student.gender === "female";
    });
  },
  // 优化二：如果匿名函数只有一句, 可以省略return
  getFemaleStudents3() {
    return this.students.filter((student) => student.gender === "female");
  },
};

/**
 * 三个输出一样
[
  { name: 'alice', gender: 'female' },
  { name: 'lily', gender: 'female' }
]
 */
console.log(students.getFemaleStudents1());
console.log(students.getFemaleStudents2());
console.log(students.getFemaleStudents3());