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This article mainly introduces the example analysis of error handling try..catch...finally+ covering throw+TypeError+RangeError in JavaScript. The article is very detailed and has certain reference value. Interested friends must read it!

1. Use

Typically, if an error occurs, the script stops immediately and the error is printed on the console.

With this statement, you can catch errors and perform reasonable actions, and you can keep the program running.

two。 Grammar

Try {/ / Code.} catch (err) {/ / err is the object / / error catch about the error details. The above code will go to this code block when the error is reported, and it will not stop running} finally {/ / whether it is thrown or caught.

This kind of statement can be nested

3. Real fuck

Catch captures all error.

If we don't know what to do with it, then we throw err.

The throw operator generates an error object.

Used to throw a user-defined exception. Execution of the current function will be stopped (statements after throw will not be executed), and control will be passed to the first Catch block in the call stack. If there is no catch block in the caller function, the program will terminate.

Example:

Throw "Error1"; / / throws an exception throw 4 with a value of a string; / / throws an exception with an integer value of 4 / * JavaScript has many built-in standard error constructors: Error,SyntaxError,ReferenceError,TypeError, etc. We can also use them to create error objects. * / let error = new Error ("Things happen ostatic O"); alert (error.name); / / Erroralert (error.message); / / exception try of Things happen o_O//json {JSON.parse ("{bad json ovalo}");} catch (e) {alert (e.name); / / SyntaxError alert (e.message); / / Unexpected token b in JSON at position 2}

Add:

The code for the try block may throw three kinds of exceptions: TypeError,RangeError,SyntaxError

Some students may not know the meaning of these three. Here's an explanation.

Both are global objects, and the global object itself does not contain any methods, but it inherits some methods through the prototype chain.

The instanceof operator is used to determine the error type:

TypeError: (type error) an error that occurs when the type of the value is not expected.

RangeError: an object indicates an error when a value is not in its allowed range or collection

SyntaxError: thrown when the Javascript language parses the code and the Javascript engine finds a tokens or token order that does not conform to the syntax specification.

Example:

Catch (e) {/ / the following are the parameter properties of this object: console.log (e instanceof TypeError); / / true console.log (e.message); / / "describe this error" console.log (e.name); / / "TypeError" console.log (e.fileName) / / "the name of the file where the code that caused the exception is located" console.log (e.lineNumber); / / the line number of the code that caused the exception} above is all the contents of the article "sample Analysis of error handling try..catch...finally+ covering throw+TypeError+RangeError in JavaScript". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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