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This article mainly explains "how to deal with accidents caused by JavaScript". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to deal with accidents caused by JavaScript".

In many programming languages, when you try to execute an illegal instruction, the code causes a run-time accident. One of the smallest illegal operations we may experience is the "divide by 0" error. JavaScript does not do this; it assigns the result variable to infinity. Other illegal operations are also common in other programming languages, including JavaScript. Accessing a null pointer or an empty object is also an example, and accessing an array element that is outside the legal scope of an array is another example.

For developers, it is usually an effort to avoid system errors. The system information is usually so vague that the average user cannot understand it. In fact, system errors can seriously affect a programmer's reputation because they are clear evidence of Bug. We want to look for these errors in the code and find them before they attack the operating system to avoid generating error messages. Looking for accidents in the code can lead to bloated code. When the language does not support unexpected handling, it is inevitable to mix normal code flow with error lookup. The following code looks for two errors-accessing an empty object and out-of-range array elements:

Var newObject = createObject (dataPiece1, dataPiece2, dataPiece3)

If (newObject = = null) {

/ / do something here when the object was not created

...

}

Else {

/ / getElementIndex return an index or-1 for an error

Var index = newObject.getElementIndex ()

If (index =-1) {

/ / handle the error case

...

}

Else {

{

/ / finally, you can do something with index

...

}

The key to supporting unexpected handling in JavaScript (as in other languages, as explained later in this article) is the try...catch statement. The Try keyword guides a piece of normal handling code that can cause unexpected events, and the Catch keyword guides a piece of unexpected handling code. Once an accident is raised in the try area, control of the program flow is switched to the first catch area that follows it. But once raised by JavaScript (which is what programmers object to), there is no mechanism to determine the type of error. The following is the try...catch code area used to simulate the above process:

Try {

Var newObject = createObject (dataPiece1, dataPiece2, dataPiece3)

Var index = newObject.getElementIndex ()

/ / do something with index

}

Catch {

Alert ("System Error; Call your sw vendor")

}

Here is another example that can actually run on your computer:

< HTML>

< HEAD>

< TITLE>

Example 1

< /TITLE>

< /HEAD>

< BODY>

< IMG SRC="doc.gif">

< SCRIPT LANGUAGE="JavaScript1.2">

< !-- try { for (image=0; image < document.images.length + 2; image++) { alert(document.images[image].border); } } catch (kuku) { alert("We have experienced a JavaScript error"); } // --> < /SCRIPT>

< /BODY>

< /HTML>

The exception performed in this example is to access an array element outside the boundary of the array. On the page (doc.gif), the number of graphs is length (1), so the maximum pointer used is length+1 (2). Notice the variable kuku passed to the catch (capture) area. JavaScript allows you to pass any variable type, which will be explained later on the page. Although we don't use this variable, you have to specify one.

Thank you for your reading, the above is the content of "how to deal with accidents caused by JavaScript". After the study of this article, I believe you have a deeper understanding of how to deal with accidents caused by JavaScript, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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