js function 返回值

function add(a, b) {
  return a + b;
}

const sum = add(3, 5); // sum 现在是 8

function fetchData(url) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(`Data from ${url}`);
    }, 1000);
  });
}

fetchData('https://example.com')
  .then(data => console.log(data)); // 一秒后打印 "Data from https://example.com"

async function fetchDataAsync(url) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(`Data from ${url}`);
    }, 1000);
  });
}

(async () => {
  const data = await fetchDataAsync('https://example.com');
  console.log(data); // 一秒后打印 "Data from https://example.com"
})();

function shouldReturnValue() {
  // 错误示例：没有返回值
}

function correctlyReturnValue() {
  return 'Hello, World!'; // 正确示例
}

// 错误示例：没有处理 Promise
fetchData('https://example.com');

// 正确示例：使用 .then()
fetchData('https://example.com').then(data => console.log(data));

// 正确示例：使用 async/await
(async () => {
  const data = await fetchDataAsync('https://example.com');
  console.log(data);
})();

function calculateSquareRoot(number) {
  if (typeof number !== 'number') {
    throw new Error('Input must be a number');
  }
  return Math.sqrt(number); // 确保返回的是数字类型
}