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It is believed that many inexperienced people have no idea about how to deeply understand JavaScript errors and stack trace. therefore, this paper summarizes the causes and solutions of the problem. I hope you can solve this problem through this article.

Sometimes people don't pay attention to these details, but this knowledge is certainly useful, especially if you are writing libraries related to testing or errors. For example, this week we have an amazing Pull Request in our chai that greatly improves the way we handle stack traces and provides more information when user assertions fail. Manipulating stack records allows you to clean up useless data and focus on important issues. In addition, when you really figure out Error and its properties, you will use it more confidently.

How stack calls work

Before we talk about errors, we must understand how stack calls work. It's very simple, but it's crucial to what we're going to delve into. If you already know this section, please feel free to skip this section.

Whenever a function is called, it is pushed to the top of the stack. After the function is executed, it is removed from the top of the stack.

The interesting thing about this data structure is that a stack will be removed from the stack, which is the familiar LIFO (last in, first out) feature.

This means that if we call function y in function x, the order in the corresponding stack is x y.

Suppose you have code like this:

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

In the above example, when the a function is executed, an is added to the top of the stack, and then when the b function is called in the a function, b is added to the top of the stack, and so on, and the same thing happens when c is called in b.

When c executes, the order of the functions in the stack is a b c

C will be removed from the top of the stack after execution, and the control flow will also be removed from the top of the stack after the execution of b, and the control flow will also be removed from the stack after execution of * *.

We can use console.trace () to better demonstrate this behavior, which prints out the records in the current stack on the console. In addition, in general, you should read stack records from top to bottom. Think about where each of the following lines of code is called.

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

Running the above code on the Node REPL server yields the following result:

Trace at c (repl:3:9) at b (repl:3:1) at a (repl:3:1) at repl:1:1 / /

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