首先，让我解释一下代码的工作原理-请参阅添加的代码中的注释：
// first you define function A and nothing happens:function A(callback) { console.log('A'); callback();}// then you define function B and nothing happens: function B() { console.log('B')}// then you define function C and nothing happens:function C() { console.log('C');}// now you call function A with argument C:A(C);// when A runs it prints 'A' and calls C before it returns// now the C runs, prints C and returns - back to A// A now has nothing more to do and returns// Now the execution continues and B can be run:B();// B runs and prints 'B'这与任何语言（如Java，C等）完全一样。
现在，第二个示例：
// first you define function A and nothing happens:function A(callback) { console.log('A'); process.nextTick(() => { callback(); });}// then you define function B and nothing happens:function B() { console.log('B')}// then you define function C and nothing happens:function C() { console.log('C');}// Then you run A with C passed as an argument:A(C);// A prints 'A' and schedules running an anonymous function:// () => { callback(); }// on the next tick of the event loop, before I/O events are handled// but after the current pre stack is unrolled// then it returns// And then B is run:B();// B prints 'B' and returns// Now nothing else is left to do so the next tick of the event loop starts// There's one function to run, scheduled earlier so it runs.// This function runs the `callback()` which was `C`// so C starts, prints 'C' and returns// The anonymous function has nothing else to do and returns// There is no more things on the event loop so the program exits更新资料
感谢Bergi解释了Zalgo的答案是什么。现在，我更好地了解了您的担忧。
这就是我们所说的zalgo吗？谁能提供给我一个实时的例子，这将导致重大故障？
我看过很多这样的代码：
function x(argument, callback) { if (!argument) { return callback(new Error('Bad argument')); } runSomeAsyncFunction(argument, (error, result) => { if (error) { return callback(new Error('Error in async function')); } callback({data: result}); });}现在，
x()如果存在错误的参数，则可以在返回之前立即运行回调，否则可以在
x()返回之后运行回调。此代码非常常见。为了测试这些论点，人们可能会争辩说应该抛出一个异常，但让我们暂时忽略一下，可能会有一些更好的操作错误示例被立即知道-
这只是一个简单的示例。
现在，如果它是这样写的：
function x(argument, callback) { if (!argument) { return process.nextTick(callback, new Error('Bad argument')); } runSomeAsyncFunction(argument, (error, result) => { if (error) { return callback(new Error('Error in async function')); } callback({data: result}); });}这样可以保证回调不会在
x()返回之前被调用。
现在，这是否可能导致“重大故障”完全取决于其使用方式。如果运行以下命令：
let a;x('arg', (err, result) => { // assume that 'a' has a value console.log(a.value);});// assign a value to 'a' here:a = {value: 10};那么它将有时版本崩溃
x()不
process.nextTick，绝不会用的版本崩溃
x()用
process.nextTick()。
