Utilisateur:Od1n/lscache.js
Apparence
Note : après avoir enregistré la page, vous devrez forcer le rechargement complet du cache de votre navigateur pour voir les changements.
Mozilla / Firefox / Konqueror / Safari : maintenez la touche Majuscule (Shift) en cliquant sur le bouton Actualiser (Reload) ou pressez Maj-Ctrl-R (Cmd-R sur Apple Mac) ;
Chrome / Internet Explorer / Opera : maintenez la touche Ctrl en cliquant sur le bouton Actualiser ou pressez Ctrl-F5.// https://github.com/pamelafox/lscache
/**
* lscache library
* Copyright (c) 2011, Pamela Fox
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*jshint undef:true, browser:true */
/**
* Creates a namespace for the lscache functions.
*/
var lscache = function() {
// Prefix for all lscache keys
var CACHE_PREFIX = 'lscache-';
// Suffix for the key name on the expiration items in localStorage
var CACHE_SUFFIX = '-cacheexpiration';
// expiration date radix (set to Base-36 for most space savings)
var EXPIRY_RADIX = 10;
// time resolution in minutes
var EXPIRY_UNITS = 60 * 1000;
// ECMAScript max Date (epoch + 1e8 days)
var MAX_DATE = Math.floor(8.64e15/EXPIRY_UNITS);
var cachedStorage;
var cachedJSON;
var cacheBucket = '';
var warnings = false;
// Determines if localStorage is supported in the browser;
// result is cached for better performance instead of being run each time.
// Feature detection is based on how Modernizr does it;
// it's not straightforward due to FF4 issues.
// It's not run at parse-time as it takes 200ms in Android.
function supportsStorage() {
var key = '__lscachetest__';
var value = key;
if (cachedStorage !== undefined) {
return cachedStorage;
}
try {
setItem(key, value);
removeItem(key);
cachedStorage = true;
} catch (exc) {
cachedStorage = false;
}
return cachedStorage;
}
// Determines if native JSON (de-)serialization is supported in the browser.
function supportsJSON() {
/*jshint eqnull:true */
if (cachedJSON === undefined) {
cachedJSON = (window.JSON != null);
}
return cachedJSON;
}
/**
* Returns the full string for the localStorage expiration item.
* @param {String} key
* @return {string}
*/
function expirationKey(key) {
return key + CACHE_SUFFIX;
}
/**
* Returns the number of minutes since the epoch.
* @return {number}
*/
function currentTime() {
return Math.floor((new Date().getTime())/EXPIRY_UNITS);
}
/**
* Wrapper functions for localStorage methods
*/
function getItem(key) {
return localStorage.getItem(CACHE_PREFIX + cacheBucket + key);
}
function setItem(key, value) {
// Fix for iPad issue - sometimes throws QUOTA_EXCEEDED_ERR on setItem.
localStorage.removeItem(CACHE_PREFIX + cacheBucket + key);
localStorage.setItem(CACHE_PREFIX + cacheBucket + key, value);
}
function removeItem(key) {
localStorage.removeItem(CACHE_PREFIX + cacheBucket + key);
}
function warn(message, err) {
if (!warnings) return;
if (!'console' in window || typeof window.console.warn !== 'function') return;
window.console.warn("lscache - " + message);
if (err) window.console.warn("lscache - The error was: " + err.message);
}
return {
/**
* Stores the value in localStorage. Expires after specified number of minutes.
* @param {string} key
* @param {Object|string} value
* @param {number} time
*/
set: function(key, value, time) {
if (!supportsStorage()) return;
// If we don't get a string value, try to stringify
// In future, localStorage may properly support storing non-strings
// and this can be removed.
if (typeof value !== 'string') {
if (!supportsJSON()) return;
try {
value = JSON.stringify(value);
} catch (e) {
// Sometimes we can't stringify due to circular refs
// in complex objects, so we won't bother storing then.
return;
}
}
try {
setItem(key, value);
} catch (e) {
if (e.name === 'QUOTA_EXCEEDED_ERR' || e.name === 'NS_ERROR_DOM_QUOTA_REACHED' || e.name === 'QuotaExceededError') {
// If we exceeded the quota, then we will sort
// by the expire time, and then remove the N oldest
var storedKeys = [];
var storedKey;
for (var i = 0; i < localStorage.length; i++) {
storedKey = localStorage.key(i);
if (storedKey.indexOf(CACHE_PREFIX + cacheBucket) === 0 && storedKey.indexOf(CACHE_SUFFIX) < 0) {
var mainKey = storedKey.substr((CACHE_PREFIX + cacheBucket).length);
var exprKey = expirationKey(mainKey);
var expiration = getItem(exprKey);
if (expiration) {
expiration = parseInt(expiration, EXPIRY_RADIX);
} else {
// TODO: Store date added for non-expiring items for smarter removal
expiration = MAX_DATE;
}
storedKeys.push({
key: mainKey,
size: (getItem(mainKey)||'').length,
expiration: expiration
});
}
}
// Sorts the keys with oldest expiration time last
storedKeys.sort(function(a, b) { return (b.expiration-a.expiration); });
var targetSize = (value||'').length;
while (storedKeys.length && targetSize > 0) {
storedKey = storedKeys.pop();
warn("Cache is full, removing item with key '" + key + "'");
removeItem(storedKey.key);
removeItem(expirationKey(storedKey.key));
targetSize -= storedKey.size;
}
try {
setItem(key, value);
} catch (e) {
// value may be larger than total quota
warn("Could not add item with key '" + key + "', perhaps it's too big?", e);
return;
}
} else {
// If it was some other error, just give up.
warn("Could not add item with key '" + key + "'", e);
return;
}
}
// If a time is specified, store expiration info in localStorage
if (time) {
setItem(expirationKey(key), (currentTime() + time).toString(EXPIRY_RADIX));
} else {
// In case they previously set a time, remove that info from localStorage.
removeItem(expirationKey(key));
}
},
/**
* Retrieves specified value from localStorage, if not expired.
* @param {string} key
* @return {string|Object}
*/
get: function(key) {
if (!supportsStorage()) return null;
// Return the de-serialized item if not expired
var exprKey = expirationKey(key);
var expr = getItem(exprKey);
if (expr) {
var expirationTime = parseInt(expr, EXPIRY_RADIX);
// Check if we should actually kick item out of storage
if (currentTime() >= expirationTime) {
removeItem(key);
removeItem(exprKey);
return null;
}
}
// Tries to de-serialize stored value if its an object, and returns the normal value otherwise.
var value = getItem(key);
if (!value || !supportsJSON()) {
return value;
}
try {
// We can't tell if its JSON or a string, so we try to parse
return JSON.parse(value);
} catch (e) {
// If we can't parse, it's probably because it isn't an object
return value;
}
},
/**
* Removes a value from localStorage.
* Equivalent to 'delete' in memcache, but that's a keyword in JS.
* @param {string} key
*/
remove: function(key) {
if (!supportsStorage()) return null;
removeItem(key);
removeItem(expirationKey(key));
},
/**
* Returns whether local storage is supported.
* Currently exposed for testing purposes.
* @return {boolean}
*/
supported: function() {
return supportsStorage();
},
/**
* Flushes all lscache items and expiry markers without affecting rest of localStorage
*/
flush: function() {
if (!supportsStorage()) return;
// Loop in reverse as removing items will change indices of tail
for (var i = localStorage.length-1; i >= 0 ; --i) {
var key = localStorage.key(i);
if (key.indexOf(CACHE_PREFIX + cacheBucket) === 0) {
localStorage.removeItem(key);
}
}
},
/**
* Appends CACHE_PREFIX so lscache will partition data in to different buckets.
* @param {string} bucket
*/
setBucket: function(bucket) {
cacheBucket = bucket;
},
/**
* Resets the string being appended to CACHE_PREFIX so lscache will use the default storage behavior.
*/
resetBucket: function() {
cacheBucket = '';
},
/**
* Sets whether to display warnings when an item is removed from the cache or not.
*/
enableWarnings: function(enabled) {
warnings = enabled;
}
};
}();