# Applying exception types in JavaScript

Suppose we have a function that accepts JSON with an array of data as a parameter and save each array element to a local storage:

`function saveData(json) { let arr = JSON.parse(json); for (let i = 0; i < arr.length; i++) { localStorage.setItem(i, arr[i]); } }`

In this function, an exception can occur in two places: when parsing JSON and when trying to save data to a local storage.

Let, for example, as error handling, we decided to display some message about problems:

`try { saveData('{1,2,3,4,5}'); } catch (error) { alert('any problems'); }`

Our message is, of course, good, but it doesn't differentiate the problems that have arisen. It would be more logical to display a message about what kind of problem arose.

To do this, we will distinguish by name the errors that have occurred:

`try { saveData('{1,2,3,4,5}'); } catch (error) { if (error.name == 'QuotaExceededError') { alert('ran out of storage space'); } if (error.name == 'SyntaxError') { alert('incorrect JSON'); } }`

Copy the code of my `saveData` function, and then, without looking into my code, implement the error handling I described.

On purpose, one by one, create exceptions that may occur in the `saveData` function.

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