require localStorage plugin

cache.js

/**
 * USAGE:
 * 	外部定义全局变量 RSINFO = { 'path': 'version' }
 */

(function (win) {
	var rslist,
		RSLIST_KEY = 'rslist',
        RSINFO = win.RSINFO || {},
		isLocalStorageSupported = (function() {
			var localStorageName = 'localStorage';

			try { return (localStorageName in win && win[localStorageName]) }
	    	catch(err) { return false }
		}) (),
		localStorage = win.localStorage,
		loadThroughXHR = function(url, callback) {
			var xhr = new XMLHttpRequest();

			xhr.open('GET', url, true);
			xhr.onreadystatechange = function(e) {
				// 不处理错误，有错误就抛出
				if (xhr.readyState === 4) {
					callback( xhr.responseText );
				}
			}
			xhr.send(null);
		},
		parseName = function(name) {
			var modName, ext,
				index = name.lastIndexOf('.');

			modName = name.substring(0, index);
			ext = name.substring(index + 1);

			return {
				moduleName: modName,
				ext: ext
			};
		},
		updateLocalStorage = function(url, content) {
			rslist[url] = {
				v: RSINFO[url],
				l: content.length
			};

			try {
				localStorage.setItem(url, content);
				localStorage.setItem(RSLIST_KEY, JSON.stringify( rslist ) );
			} catch(err) {}
			
		};

	// 合法性校验，清空过期和无效的js文件
	// RSINFO 由后端直接吐到页面上
	(function() {
		if (!!RSINFO && isLocalStorageSupported) {
			var k, v, isFresh;

			rslist = JSON.parse(localStorage.getItem(RSLIST_KEY)) || {};

			for (k in RSINFO) {
				isFresh = RSINFO.hasOwnProperty(k) && (rslist.hasOwnProperty(k)
					// 判断版本号一致
					&& (v = RSINFO[k]) == rslist[k].v 	
				 	// 校验文件长度一致 
					&& (localStorage[k].length == rslist[k].l));

				if (!isFresh) {
					delete rslist[k];
					localStorage.removeItem(k);
				}
			}
			localStorage.setItem(RSLIST_KEY, rslist);
		}

	}) ();

	define({
		load: function(name, req, load, config) {
			if (config.isBuild) {
				load();
				return;
			}

			var cached,
				parsed = parseName(name),
				url = req.toUrl(name);

			if (isLocalStorageSupported) {
				cached = localStorage[url];

				if (cached) {
					load.fromText(cached);

				} else {
					loadThroughXHR(url, function(content) {
						if (parsed.ext === 'js')
							content += '\n //@ sourceURL=' + name;

						load.fromText(content);							
						updateLocalStorage(url, content);
					});

					return;
				}
			}

			req([name], function (content) {
	            load(content);
	        });
		}
	});
}) (window);