Storage

The Storage interface of the Web Storage API provides access to the session storage or local storage for a particular domain, allowing you to for example add, modify or delete stored data items.

If you want to manipulate the session storage for a domain, you call Window.sessionStorage method; If you want to manipulate the local storage for a domain, you call Window.localStorage.

Properties

Storage.length Read only

Returns an integer representing the number of data items stored in the Storage object.

Methods

Storage.key()

When passed a number n, this method will return the name of the nth key in the storage.

Storage.getItem()

When passed a key name, will return that key's value.

Storage.setItem()

When passed a key name and value, will add that key to the storage, or update that key's value if it already exists.

Storage.removeItem()

When passed a key name, will remove that key from the storage.

Storage.clear()

When invoked, will empty all keys out of the storage.

Examples

Here we access a Storage object by calling localStorage. We first test whether the local storage contains data items using !localStorage.getItem('bgcolor'). If it does, we run a function called setStyles() that grabs the data items using Storage.getItem() and uses those values to update page styles. If it doesn't, we run another function, populateStorage(), which uses Storage.setItem() to set the item values, then runs setStyles().

if(!localStorage.getItem('bgcolor')) {
  populateStorage();
}
setStyles();

function populateStorage() {
  localStorage.setItem('bgcolor', document.getElementById('bgcolor').value);
  localStorage.setItem('font', document.getElementById('font').value);
  localStorage.setItem('image', document.getElementById('image').value);
}

function setStyles() {
  var currentColor = localStorage.getItem('bgcolor');
  var currentFont = localStorage.getItem('font');
  var currentImage = localStorage.getItem('image');

  document.getElementById('bgcolor').value = currentColor;
  document.getElementById('font').value = currentFont;
  document.getElementById('image').value = currentImage;

  htmlElem.style.backgroundColor = '#' + currentColor;
  pElem.style.fontFamily = currentFont;
  imgElem.setAttribute('src', currentImage);
}

Specifications

Specification	Status	Comment
Web Storage (Second edition) The definition of 'Storage' in that specification.	Recommendation

Browser compatibility

[1] Since iOS 5.1, Safari Mobile stores localStorage data in the cache folder, which is subject to occasional clean up at the behest of the OS, typically if space is short.

All browsers have varying capacity levels for both localStorage and sessionStorage. Here is a detailed rundown of all the storage capacities for various browsers.

See also

Using the Web Storage API