How does try catch work

A catch -block contains statements that specify what to do if an exception is thrown in the try -block. If any statement within the try -block or in a function called from within the try -block throws an exception, control is immediately shifted to the catch -block. If no exception is thrown in the try -block, the catch -block is skipped. The finally -block will always execute after the try -block and catch -block s have finished executing. It always executes, regardless of whether an exception was thrown or caught.

You can nest one or more try statements. If an inner try statement does not have a catch -block, the enclosing try statement's catch -block is used instead. You can also use the try statement to handle JavaScript exceptions. When a catch -block is used, the catch -block is executed when any exception is thrown from within the try -block.

For example, when the exception occurs in the following code, control transfers to the catch -block. The catch -block specifies an identifier e in the example above that holds the value of the exception; this value is only available in the scope of the catch -block. You can create "Conditional catch -blocks" by combining try A common use case for this is to only catch and silence a small subset of expected errors, and then re-throw the error in other cases:.

Improve this question. Jakub M. Hm, you are right, I didn't notice throw : but the rest of the questions is still valid — Jakub M. Add a comment. Active Oldest Votes. Improve this answer. Redtama 1, 1 1 gold badge 13 13 silver badges 34 34 bronze badges. Alexei Kaigorodov Alexei Kaigorodov Mehdi Varse Mehdi Varse 1 1 silver badge 12 12 bronze badges. Sign up or log in Sign up using Google.

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Related Hot Network Questions. Question feed. In this case, finally is executed just before the control returns to the outer code. But finally works before the execution flow leaves the function. Like a programming error or some other terrible thing. Is there a way to react on such occurrences? For instance, Node. And in the browser we can assign a function to the special window. The role of the global handler window. There may be no catch section or no finally , so shorter constructs try We can also generate our own errors using the throw operator.

More on extending errors in the next chapter. Is there an advantage here in using finally or both code fragments are equal? If there is such an advantage, then give an example when it matters.

The finally clause works in case of any exit from try We want to make this open-source project available for people all around the world. Tutorial map. A recent addition. This is a recent addition to the language. Old browsers may need polyfills. Variables are local inside try The information from this section is not a part of the core JavaScript. Tasks Finally or just the code? Compare the two code fragments. The first one uses finally to execute the code after try The difference becomes obvious when we look at the code inside a function.

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