JS try catch基本用法以及常见的异常处理

try {
  // 可能会抛出异常的代码块
} catch (error) {
  // 捕获到异常后执行的代码
}

try {
  let num = 10;
  let result = num / 0;
  console.log(result); // Infinity
} catch (error) {
  console.log("An error occurred:", error);
}

function divide(a, b) {
  try {
    if (b === 0) {
      throw new Error("Division by zero is not allowed!");
    }
    return a / b;
  } catch (error) {
    console.log("Error:", error.message);
    return null;  // 返回 null 以表示错误
  }
}

console.log(divide(10, 2)); // 5
console.log(divide(10, 0)); // Error: Division by zero is not allowed! null

try {
  let user = null;
  if (!user) {
    throw new TypeError("User is not defined");
  }
} catch (error) {
  if (error instanceof TypeError) {
    console.log("TypeError caught:", error.message);
  } else {
    console.log("Other error caught:", error.message);
  }
}

function fetchData(url) {
  let connection = null;
  
  try {
    connection = openConnection(url);  // 假设这是一个开连接的操作
    let data = connection.requestData();  // 假设这是一项网络请求操作
    return data;
  } catch (error) {
    console.error("Error fetching data:", error);
  } finally {
    if (connection) {
      connection.close();  // 确保无论如何都关闭连接
      console.log("Connection closed.");
    }
  }
}

async function fetchData() {
  try {
    let response = await fetch('https://api.example.com/data');
    if (!response.ok) {
      throw new Error('Network response was not ok');
    }
    let data = await response.json();
    return data;
  } catch (error) {
    console.error("Fetching data failed:", error.message);
  }
}

fetchData();

try {
  try {
    let num = 10;
    if (num > 5) {
      throw new Error("Number is too large");
    }
  } catch (error) {
    console.log("Handling error:", error.message);
    throw error; // 重新抛出异常
  }
} catch (error) {
  console.log("Caught the re-thrown error:", error.message);
}