Feature: #84780 - Remove entries in localStorage by key prefix

Description

The localStorage wrapper TYPO3/CMS/Backend/Storage/Client is now capable of removing entries in the localStorage by a specific key prefix.

Impact

The method Client.unsetByPrefix() takes the prefix as argument. As all keys are internally namespaced with a t3- prefix, this must be omitted in the requested prefix.

Example:

function foo() {
    // Removes any localStorage entry whose key starts with "t3-bar-"
    Client.unsetByPrefix('bar-');
}