如何在js中正确制作.map

// 基本用法
const numbers = [1, 2, 3, 4];
const doubled = numbers.map(function(num) {
  return num * 2;
});
console.log(doubled); // 输出: [2, 4, 6, 8]

// 链式调用
const numbers = [1, 2, 3, 4];
const result = numbers
  .map(num => num * 2)
  .filter(num => num > 5);
console.log(result); // 输出: [6, 8]

// 处理对象数组
const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
];
const names = users.map(user => user.name);
console.log(names); // 输出: ['Alice', 'Bob', 'Charlie']

const numbers = [1, 2, 3];
const doubled = numbers.map(num => {
  num * 2; // 缺少 return 语句
});
console.log(doubled); // 输出: [undefined, undefined, undefined]

const numbers = [1, 2, 3];
const doubled = numbers.map(num => num * 2);
console.log(doubled); // 输出: [2, 4, 6]

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];
const names = users.map(user => user.age); // user.age 是 undefined
console.log(names); // 输出: [undefined, undefined]

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];
const names = users.map(user => user.name);
console.log(names); // 输出: ['Alice', 'Bob']