QJavaScript · Interview preparation
How is sessionStorage different from localStorage?
sessionStorage is scoped to a particular browser tab's page session, while localStorage persists until cleared.
The idea to remember.
sessionStorage is scoped to a particular browser tab's page session, while localStorage persists until cleared. Both are synchronous and accessible to JavaScript running on the origin.
01Learn by doing
From first example to real project.
Start with the smallest working idea, examine a more detailed example, then look at a real application pattern. Adapt dependencies, error handling and data models to your project.
Basic: delegate one listener
01 / BEGINNERA parent can handle events from matching children.
document.querySelector('#list').addEventListener('click', event => {
const button = event.target.closest('button[data-id]');
if (button) console.log(button.dataset.id);
});Intermediate: respect request lifecycles
02 / INTERMEDIATEAbort a pending request when it is no longer needed.
const controller = new AbortController();
fetch('/api/items', { signal: controller.signal });
// When the user navigates away:
controller.abort();Real scenario: safe persisted preferences
03 / REAL SCENARIOValidate stored data instead of assuming it is trustworthy.
function readTheme() {
const stored = localStorage.getItem('theme');
return stored === 'dark' ? 'dark' : 'light';
}
function saveTheme(theme) {
if (theme === 'dark' || theme === 'light') localStorage.setItem('theme', theme);
}02Check your understanding
Try it in your own words.
Explain how is sessionStorage different from localStorage without looking at the code. Then modify the intermediate example, describe one trade-off and identify when the real-world pattern fits.
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