JavaScript錯(cuò)誤處理和堆棧追蹤詳解

function c() {
  console.log('c');
}
 
function b() {
  console.log('b');
  c();
}
 
function a() {
  console.log('a');
  b();
}
 
a();

function c() {
  console.log('c');
  console.trace();
}
 
function b() {
  console.log('b');
  c();
}
 
function a() {
  console.log('a');
  b();
}
 
a();

Trace
  at c (repl:3:9)
  at b (repl:3:1)
  at a (repl:3:1)
  at repl:1:1 // <-- For now feel free to ignore anything below this point, these are Node's internals
  at realRunInThisContextScript (vm.js:22:35)
  at sigintHandlersWrap (vm.js:98:12)
  at ContextifyScript.Script.runInThisContext (vm.js:24:12)
  at REPLServer.defaultEval (repl.js:313:29)
  at bound (domain.js:280:14)
  at REPLServer.runBound [as eval] (domain.js:293:12)

function c() {
  console.log('c');
}
 
function b() {
  console.log('b');
  c();
  console.trace();
}
 
function a() {
  console.log('a');
  b();
}

Trace
  at b (repl:4:9)
  at a (repl:3:1)
  at repl:1:1 // <-- For now feel free to ignore anything below this point, these are Node's internals
  at realRunInThisContextScript (vm.js:22:35)
  at sigintHandlersWrap (vm.js:98:12)
  at ContextifyScript.Script.runInThisContext (vm.js:24:12)
  at REPLServer.defaultEval (repl.js:313:29)
  at bound (domain.js:280:14)
  at REPLServer.runBound [as eval] (domain.js:293:12)
  at REPLServer.onLine (repl.js:513:10)

try {
  try {
    throw new Error('Nested error.'); // The error thrown here will be caught by its own `catch` clause
  } catch (nestedErr) {
    console.log('Nested catch'); // This runs
  }
} catch (err) {
  console.log('This will not run.');
}

try {
  throw new Error('First error');
} catch (err) {
  console.log('First catch running');
  try {
    throw new Error('Second error');
  } catch (nestedErr) {
    console.log('Second catch running.');
  }
}
try {
  console.log('The try block is running...');
} finally {
  try {
    throw new Error('Error inside finally.');
  } catch (err) {
    console.log('Caught an error inside the finally block.');
  }
}

function runWithoutThrowing(func) {
  try {
    func();
  } catch (e) {
    console.log('There was an error, but I will not throw it.');
    console.log('The error\'s message was: ' + e.message)
  }
}
 
function funcThatThrowsError() {
  throw new TypeError('I am a TypeError.');
}
 
runWithoutThrowing(funcThatThrowsError);

function runWithoutThrowing(func) {
  try {
    func();
  } catch (e) {
    console.log('There was an error, but I will not throw it.');
    console.log('The error\'s message was: ' + e.message)
  }
}
 
function funcThatThrowsString() {
  throw 'I am a String.';
}
 
runWithoutThrowing(funcThatThrowsString);

const fs = require('fs');
 
fs.readdir('/example/i-do-not-exist', function callback(err, dirs) {
  if (err instanceof Error) {
    // `readdir` will throw an error because that directory does not exist
    // We will now be able to use the error object passed by it in our callback function
    console.log('Error Message: ' + err.message);
    console.log('See? We can use Errors without using try statements.');
  } else {
    console.log(dirs);
  }
});

new Promise(function(resolve, reject) {
  reject(new Error('The promise was rejected.'));
}).then(function() {
  console.log('I am an error.');
}).catch(function(err) {
  if (err instanceof Error) {
    console.log('The promise was rejected with an error.');
    console.log('Error Message: ' + err.message);
  }
});

const myObj = {};
 
function c() {
}
 
function b() {
  // Here we will store the current stack trace into myObj
  Error.captureStackTrace(myObj);
  c();
}
 
function a() {
  b();
}
 
// First we will call these functions
a();
 
// Now let's see what is the stack trace stored into myObj.stack
console.log(myObj.stack);
 
// This will print the following stack to the console:
//  at b (repl:3:7) <-- Since it was called inside B, the B call is the last entry in the stack
//  at a (repl:2:1)
//  at repl:1:1 <-- Node internals below this line
//  at realRunInThisContextScript (vm.js:22:35)
//  at sigintHandlersWrap (vm.js:98:12)
//  at ContextifyScript.Script.runInThisContext (vm.js:24:12)
//  at REPLServer.defaultEval (repl.js:313:29)
//  at bound (domain.js:280:14)
//  at REPLServer.runBound [as eval] (domain.js:293:12)
//  at REPLServer.onLine (repl.js:513:10)

const myObj = {};
 
function d() {
  // Here we will store the current stack trace into myObj
  // This time we will hide all the frames after `b` and `b` itself
  Error.captureStackTrace(myObj, b);
}
 
function c() {
  d();
}
 
function b() {
  c();
}
 
function a() {
  b();
}
 
// First we will call these functions
a();
 
// Now let's see what is the stack trace stored into myObj.stack
console.log(myObj.stack);
 
// This will print the following stack to the console:
//  at a (repl:2:1) <-- As you can see here we only get frames before `b` was called
//  at repl:1:1 <-- Node internals below this line
//  at realRunInThisContextScript (vm.js:22:35)
//  at sigintHandlersWrap (vm.js:98:12)
//  at ContextifyScript.Script.runInThisContext (vm.js:24:12)
//  at REPLServer.defaultEval (repl.js:313:29)
//  at bound (domain.js:280:14)
//  at REPLServer.runBound [as eval] (domain.js:293:12)
//  at REPLServer.onLine (repl.js:513:10)
//  at emitOne (events.js:101:20)