JavaScript数组filter()方法详解：语法、数据筛选与链式调用实战

// 示例1：筛选数组中的偶数
const numbers = [1, 2, 3, 4, 5, 6];
const evenNumbers = numbers.filter(number => number % 2 === 0);
console.log(evenNumbers); // [2, 4, 6]

// 示例2：筛选出高价值客户
const customers = [
  { id: 1, name: 'Alice', orders: [
    { amount: 1200, date: '2023-05-15' },
    { amount: 2500, date: '2023-07-22' },
    { amount: 1800, date: '2023-08-05' }
  ]},
  { id: 2, name: 'Bob', orders: [
    { amount: 9000, date: '2023-03-01' },
    { amount: 2200, date: '2023-09-12' }
  ]},
  { id: 3, name: 'Charlie', orders: [
    { amount: 750, date: '2023-02-17' },
    { amount: 1100, date: '2023-04-03' },
    { amount: 1500, date: '2023-05-09' },
    { amount: 1300, date: '2023-06-21' }
  ]},
  { id: 4, name: 'David', orders: [
    { amount: 2000, date: '2023-01-05' },
    { amount: 1700, date: '2023-02-20' },
    { amount: 2300, date: '2023-03-18' }
  ]},
  { id: 5, name: 'Eve', orders: [
    { amount: 3500, date: '2023-04-08' },
    { amount: 4200, date: '2023-05-22' }
  ]},
  { id: 6, name: 'Frank', orders: [
    { amount: 550, date: '2023-03-02' },
    { amount: 850, date: '2023-08-16' }
  ]},
  // ... 更多客户
];
const highValueCustomers = customers.filter(customer => {
  const totalSpent = customer.orders.reduce((sum, order) => {
    const orderDate = new Date(order.date);
    const oneYearAgo = new Date();
    oneYearAgo.setFullYear(oneYearAgo.getFullYear() - 1);
    return sum + (orderDate >= oneYearAgo ? order.amount : 0);
  }, 0);
  return totalSpent > 10000 && customer.orders.length > 5;
});
console.log(highValueCustomers);

// 示例3：移除无效的用户记录
const users = [
  { id: 1, name: 'Alice', email: 'alice', password: 'alice123' },
  { id: 2, name: 'Bob', email: 'bob@example.com', password: 'b' },
  { id: 3, name: 'Charlie', email: 'charlie@work.com', password: 'Ch@rl1e!' },
  { id: 4, name: 'Diana', email: 'diana', password: 'D123456' },
  { id: 5, name: 'Edward', email: 'edward@', password: 'edwardpassword' },
  { id: 6, name: 'Fiona', email: 'fiona123', password: 'fionaP@ss' },
  { id: 7, name: 'George', email: 'george@example.com', password: 'g' },
  { id: 8, name: 'Hannah', email: 'hannah@hann.com', password: 'HannahPass123!' },
  { id: 9, name: 'Ivan', email: 'ivan', password: 'IvanIvanIvan' },
  { id: 10, name: 'Julia', email: 'julia@julia', password: 'ju@123' },
  // ... 更多用户
];
const validUsers = users.filter(user => {
  // 使用正则表达式验证邮箱格式
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  // 密码长度至少为6个字符
  return emailRegex.test(user.email) && user.password.length >= 6;
});
console.log(validUsers);

// 示例4：计算员工的平均薪资增长
const employees = [
  { id: 1, name: 'Alice', salary: 5000, salaryTwoYearsAgo: 4000 },
  { id: 2, name: 'Bob', salary: 6500, salaryTwoYearsAgo: 7000 },
  { id: 3, name: 'Charlie', salary: 8000, salaryTwoYearsAgo: 6500 },
  { id: 4, name: 'David', salary: 7200, salaryTwoYearsAgo: 6000 },
  { id: 5, name: 'Eve', salary: 9500, salaryTwoYearsAgo: 8200 },
  { id: 6, name: 'Frank', salary: 6800, salaryTwoYearsAgo: 5800 },
  { id: 7, name: 'Grace', salary: 7800, salaryTwoYearsAgo: 7200 },
  { id: 8, name: 'Heidi', salary: 9200, salaryTwoYearsAgo: 8500 },
  { id: 9, name: 'Ivan', salary: 6300, salaryTwoYearsAgo: 5500 },
  { id: 10, name: 'Judy', salary: 8600, salaryTwoYearsAgo: 7800 },
  // ... 更多员工
];
const averageSalaryGrowth = employees
  .filter(employee => {
    const growth = (employee.salary - employee.salaryTwoYearsAgo) / employee.salaryTwoYearsAgo;
    return growth > 0.10;
  })
  .map(employee => {
    const growth = (employee.salary - employee.salaryTwoYearsAgo) / employee.salaryTwoYearsAgo;
    return growth * 100; // 转换为百分比
  })
  .reduce((totalGrowth, growth) => totalGrowth + growth, 0) / employees.length;
console.log(`The average salary growth over the past two years is: ${averageSalaryGrowth.toFixed(2)}%`);