Web Storage QuotaExceededError

When storage limits exceeds on this function window.sessionStorage.setItem(key, value);, it throws a "QuotaExceededError" DOMException exception if the new value couldn't be set. (Setting could fail if, e.g., the user has disabled storage for the site, or if the quota has been exceeded.)

HTML

<button type="button" id="fill-button">Fill sessionStorage</button><br>
<button type="button" id="clear-button">Clear sessionStorage</button>

JavaScript

/* global window, document */
var exampleString = 'Let\'s save a string into many different storage items, until the storage quote is exceeded.',
counter = 0,
/** tries to write a value into a sessionStorage key. Alerts any error */
writeString = function (key, value) {
    try {
        window.sessionStorage.setItem(key, value);
        return false;
    } catch (error) {
        window.alert(error);
        return false;
    }
    return true;
},
fillButtonClickHandler = function () {
    /** increase the key number for sessionStorage, until writeStringHandler returns false */
    while (writeString('key_' + counter, exampleString)) {
        counter += 1;
    }
},
clearButtonClickHandler = function () {
    window.sessionStorage.clear();
    counter = 0;
};

document.getElementById('fill-button').addEventListener('click', fillButtonClickHandler);
document.getElementById('clear-button').addEventListener('click', clearButtonClickHandler);