JavaScript Error Handling Pit Avoidance Guide

1. Error Type: Three "killers" and coping strategies

1. SyntaxError (SyntaxError)

• feature: The code parsing stage directly reported an error, such as missing brackets and incorrect spelling of keywords.
• Example：

("Hello World';  // Closed quotes are missing  

• Solution：
  • Use tools such as ESLint to detect statically.
  • Avoid relying on semicolons to automatically insert and explicitly write semicolons.

2. Runtime Error (Runtime Error)

• Typical subclasses：
  • ReferenceError: Access undeclared variables (e.g.(undeclaredVar)）。
  • TypeError: Perform an operation on the error type (e.g.()）。
  • RangeError: The value goes beyond the boundary (such asnew Array(-1)）。
• Debugging Tips：
  • Using Chrome DevToolsBreakpoint debuggingandCall stack trace。

3. Logical Error

• Concealment: The code has no errors but the result is abnormal, such as multiplication is misused instead of addition.
• Defense Plan：
  • Write unit test coverage boundary conditions.
  • use()Make runtime assertions.

2. Core processing mechanism: the "three tricks" of try/catch

1. Infrastructure

try {  
  let num = ('{invalid json}'); 
  (num);
} catch (error) {  
  ("Catch Error:", );  
} finally {  
  cleanupResources();  // It will be executed regardless of success or failure}  

2. Custom error: accurate positioning problem

Throw a semantic error：

class NetworkError extends Error {  
  constructor(url) {  
    super(`ask ${url} fail`);  
     = "NETWORK_FAILURE";  
  }  
}  
throw new NetworkError("");  

Advantages: ByClassification handles different errors.

3. Performance Trap

Avoid abuse of try/catch within loops: V8 engine pairtryBlock optimization is weak, and high-frequency calls may slow down performance.

// Error demonstration:for (let i = 0; i < 1e6; i++) {  
  try { /* Possible failure operation */ }  
  catch {}  
}  
// Correct way: Move the try/catch to the outer layer of the loop

3. Asynchronous error handling: "reef" between Promise and async/await

1. Promise not caught error

• Typical scenarios：

fetchData().then(res => { ... }); // Missing .catch()

• • Consequence: TriggerUncaught (in promise) Error, causing a global crash.
• Solution：
  • Chain processing：.then().catch()。
  • Global guarantee：

('unhandledrejection', e => {  
  reportToServer();  // Report to the monitoring system});  

2. Elegant treatment of async/await

• Combined with try/catch：

async function loadUserData() {  
  try {  
    const data = await fetch('/api/user');  
    if (!) throw new Error('Status code exception');  
  } catch (error) {  
    showToast(`Loading failed：${}`);  
  }  
}  

• Advantages: Synchronize error handling logic to avoid callback hell.

This is the article about JavaScript error handling guide to avoid pitfalls. For more related JavaScript error handling content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!