Exception
is an event that disrupts the normal flow of execution. JavaScript provides
try...catch...finally statements to handle the exceptions.
Syntax
try{
}catch(exception_object){
}finally{
}
try block
contains one (or) more statements followed by at least one catch clause or a
finally clause, or both. So you can use try...catch...finally block in any one
of the following three forms.
a. try followed by catch
try{
}catch(exception_object){
}
b. try followed by finally
try{
}finally{
}
c. try followed by catch and finally
try{
}catch(exception_object){
}finally{
}
try block
The first
step to handle the exception is enclose the error prone code in the try block.
A try block must have at least followed by catch or finally block.
catch block
catch
block handles the exceptions that are thrown inside the try block.
finally block
The
finally block always executes when the try block exits. This ensures that the
finally block is executed even if an unexpected exception occurs. Finally block
mainly used to perform clean up operations. If there is no local catch block to
handle the exception, the interpreter first executes the finally block and then
jumps to the nearest containing catch clause.
exceptionHandle.html
<!DOCTYPE html> <html> <head> <title>for in loop Example</title> </head> <body> <script> function factorial(n) { if (n < 0) { throw new Error("n should be >= 0"); } if (n == 0 || n == 1) return 1; return n * factorial(n - 1); } try { factorial(-10); } catch (e) { document.write(e); } </script> </body> </html>
Open above
page in browser, you can able to see following kind of text.
Error: n
should be >= 0
Is try statements nested?
Yes, you
can embed one try statement in other. If an inner try statement does not have a
catch clause, the enclosing try statement's catch clause is entered.
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