20个拿来就能用的JavaScript技巧分享

const person = { name: 'Alice', age: 30 };
const { name, age } = person;
console.log(name); // Output: Alice
console.log(age); // Output: 30

const originalArray = [1, 2, 3];
const clonedArray = [...originalArray];
console.log(clonedArray); // Output: [1, 2, 3]

const obj1 = { a: 1, b: 2 };
const obj2 = { b: 3, c: 4 };
const merged = { ...obj1, ...obj2 };
console.log(merged); // Output: { a: 1, b: 3, c: 4 }

const numbers = [1, 2, 3];
const squared = numbers.map(num => num * num);
console.log(squared); // Output: [1, 4, 9]

const name = user.name || 'Guest';
console.log(name); // Output: Guest

function delayedLog(message, time) {
  setTimeout(() => {
    console.log(message);
  }, time);
}
delayedLog('Hello', 1000); // Output (after 1 second): Hello

const greet = name => `Hello, ${name}!`;
console.log(greet('Alice')); // Output: Hello, Alice!

const promise1 = fetch('url1');
const promise2 = fetch('url2');
Promise.all([promise1, promise2])
  .then(responses => console.log(responses))
  .catch(error => console.error(error));

const key = 'name';
const person = { [key]: 'Alice' };
console.log(person.name); // Output: Alice

const name = 'Alice';
const greeting = `Hello, ${name}!`;
console.log(greeting); // Output: Hello, Alice!

const notANumber = 'Not a number';
console.log(Number.isNaN(notANumber)); // Output: false

const user = { info: { name: 'Alice' } };
console.log(user.info?.age); // Output: undefined

const text = 'Hello, world!';
const pattern = /Hello/g;
console.log(text.match(pattern)); // Output: ['Hello']

const data = '{"age":"30"}';
const parsed = JSON.parse(data, (key, value) => {
  if (key === 'age') return Number(value);
  return value;
});
console.log(parsed.age); // Output: 30

const users = [{ name: 'Alice' }, { name: 'Bob' }];
console.table(users);
console.groupCollapsed('Details');
console.log('Name: Alice');
console.log('Age: 30');
console.groupEnd();

async function fetchData() {
  try {
    const response = await fetch('url');
    const data = await response.json();
    console.log(data);
  } catch (error) {
    console.error(error);
  }
}

fetchData();

function createCounter() {
  let count = 0;
  return function () {
    count++;
    console.log(count);
  };
}

const counter = createCounter();
counter(); // Output: 1
counter(); // Output: 2

function fibonacci(n, memo = {}) {
  if (n in memo) return memo[n];
  if (n <= 2) return 1;
  memo[n] = fibonacci(n - 1, memo) + fibonacci(n - 2, memo);
  return memo[n];
}

console.log(fibonacci(10)); // Output: 55

const observer = new IntersectionObserver(entries => {
  entries.forEach(entry => {
    if (entry.isIntersecting) {
      entry.target.classList.add('fade-in');
      observer.unobserve(entry.target);
    }
  });
});

const elements = document.querySelectorAll('.animate');
elements.forEach(element => observer.observe(element));

// math.js
export function add(a, b) {
  return a + b;
}

// app.js
import { add } from './math.js';
console.log(add(2, 3)); // Output: 5

const handler = {
  get(target, prop) {
    return `Property "${prop}" doesn't exist.`;
  }
};

const proxy = new Proxy({}, handler);
console.log(proxy.name); // Output: Property "name" doesn't exist.