HTML Web Storage
With web storage, web applications can store data locally within the user's browser. Before HTML5, application data had to be stored in cookies, included in every server request. Web storage is more secure, and large amounts of data can be stored locally, without affecting website performance.
HTML Web Storage Objects
HTML web storage provides two objects for storing data on the client:
- window.localStorage - stores data with no expiration date
- window.sessionStorage - stores data for one session (data is lost when the browser tab is closed)
Before using web storage, check browser support for localStorage and sessionStorage:
if (typeof(Storage) !== "undefined") {
// Code for localStorage/sessionStorage.
} else {
// Sorry! No Web Storage support..
}The localStorage Object
The localStorage object stores the data with no expiration date. The data will not be deleted when the browser is closed, and will be available the next day, week, or year.
// Store
localStorage.setItem("lastname", "Smith");
// Retrieve
document.getElementById("result").innerHTML = localStorage.getItem("lastname");The sessionStorage Object
The sessionStorage object is equal to the localStorage object, except that it stores the data for only one session. The data is deleted when the user closes the specific browser tab.
The following example counts the number of times a user has clicked a button, in the current session:if (sessionStorage.clickcount) {
sessionStorage.clickcount = Number(sessionStorage.clickcount) + 1;
} else {
sessionStorage.clickcount = 1;
}
document.getElementById("result").innerHTML = "You have clicked the button " +
sessionStorage.clickcount + " time(s) in this session.";