


What is the use of js try...catch syntax structure? try...catch detailed explanation
What this article brings to you is what is the use of js try...catch syntax structure? Detailed explanation of try...catch. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
1. The basic syntax of try...catch
try..catch construction mainly has two blocks: try{ } and catch(err){}:
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The working principle is as follows:
1. First, execute the code try {...}.
2. If there is no error, ignore catch(err){....}. After executing try {...}, skip catch(err){....} and execute directly. Next statement.
3. If an error occurs, try stops executing and starts executing catch(err){...}. The err variable (which can be defined arbitrarily) contains an error object detailing what happened.
2. Error Object
When an error occurs, JavaScript will generate an object containing detailed information about it. This object is then passed to catch as a parameter, for example:
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For all built-in errors, the error object inside the catch block has two main properties:
name
Error name, "reference error" for an undefined variable.
message
Text message with error details.
There are other non-standard properties in most environments. The most widely used and supported one is:
stack
Current call stack: a string containing information about the nested sequence of calls that caused the error (the purpose of which is for debugging).
For example:
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3. Use "try...catch"
Let us explore a real Use case try..catch.
html code:
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js code:
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Rendering after operation:
4. try...catch...finally
The try...catch construct also has a code clause: finally.
If it exists, it will run in all cases:
1. After try, if there is no error,
2. After catch After that, if there is an error
The extended syntax looks like this:
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Try running this code:
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The code can be executed in two ways:
If you answer "Yes (OK)" to "Made a mistake?", then execute try -> catch -> finally.
If you say "No (cancel)", then try -> finally.
finally indicates that we need to use this clause when we start doing something before try..catch and want to complete it without any result.
For example, we want to measure the time fib(n) taken by the Fibonacci number function. Of course, we can start the measurement before running it and complete it afterwards. But what if an error occurs during the function call? In particular, the implementation of fib(n) in the code below returns an error for a negative or non-integer number.
finally Regardless, this clause is a good place to get your measurements done.
Here finally guarantees that the time will be measured correctly in both cases - if fib is executed successfully and an error occurs:
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When we enter 35:
When we enter -1:
Both measurements are completed correctly.
Summary: The above is the entire content of this article. I hope it will be helpful to everyone’s learning. Related video tutorials are recommended: JavaScript Tutorial!
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