Storage - Web APIs 编辑

The Storage interface of the Web Storage API provides access to a particular domain's session or local storage. It allows, for example, the addition, modification, or deletion of stored data items.

To manipulate, for instance, the session storage for a domain, a call to Window.sessionStorage is made; whereas for local storage the call is made to 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();
} else {
  setStyles();
}

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

  setStyles();
}

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);
}

Note: To see this running as a complete working example, see our Web Storage Demo.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using the Web Storage API
• Window.localStorage
• Window.sessionStorage
• CacheStorage