JavaScript error Try-Catch statement; Through this tutorial, i am going to explain you in detail about JavaScript try...catch
statement and it’s usage with examples.
Because while developing the web and the app, some error remains. Usually, at that time script execution halt., If you will use try...catch
statement in your js script, so this will help you to print errors to console.
JavaScript try...catch
statement
The try…catch statement is used to handle errors in the js script.
The following syntax represents the try...catch
statement:
try { // code may cause error } catch(error){ // code to handle error }
The demonstration of above given program; as shown below:
- Execute the code in
try {...}
statement - If not come to errors in the script, then
catch(err)
is ignored: the execution arrives at the finish oftry
and goes on, skippingcatch
. - If an error occurs,
try
execution is stopped and jumps to thecatch
block. - If you want to see what error happened, you can access an
error
object and display errors inside acatch
block.
So far, you have seen the above given syntax of try...catch
and what it works.
But now you will learn by try...catch
example and also will see the flowchart of try-catch, how work it.
Example 1 – Try-Catch Statement in JavaScript
Let’s take a look an example of try...catch
statement. as shown below:
try { myFunction(); } catch(error){ console.log(error); // print error object }
Output
ReferenceError: myFunction is not defined
When you run the above example script, it display error myFunction()
function doesn’t exist, therefore, JavaScript throws an error.
In javascript, the error object has two main properties:
- Error name
- Error message
If you are using a try..catch
statement. And you want to print the custom in your script and program. So for this you have to use try/throw/catch
statements.
Let’s take a look example using try/throw/catch
statements:
try{ throw new Error ('This is a new error') } catch(error){ console.log(error) console.log("End of try-catch block") }
Output
Error: This is a new error
This example shows how you can create our own error in the throw
block. Then try
the code which should throw
an error which should be caught by the catch
block.
Example 2 – JavaScript try/catch/finally statement
The try..catch
statement has one more clause finally
. This is a optional clause and it runs in all situations.
In other words, The piece of code always executes, which is written inside finally
block.
The following syntax represents the try…catch…finally statement:
try { ... try to execute the code ... } catch(e) { ... handle errors ... } finally { ... execute always ... }
Let’s take a look the following example:
function myFunc(){ try { return 'try'; } catch(error) { return 'catch'; } finally { return 'finally'; } } console.log(myFunc());
Output
finally
Run the above script, it will return “finally” as output. Because no error happens in the try
block. However, the try block to be ignored.
Note that two important points, if you are using try…catch…finally statement:
- If you remove the
finally
clause, themyFunction()
function will return ‘first’ as output. - Once you use the
finally
clause, thecatch
clause becomes optional.
Note that, The try..catch
statement works to handle errors in a js script.
Conclusion
In this tutorial, you have learned everything about JavaScript try...catch
statement as well as finally
statement and using this how to handle errors in javascript