应用web sql适配local storage存储

使用web sql适配local storage存储
/*** Begin class defination XDB : Web sql辅助方法*/var XDB = {db: null, init: function(dbName, version, dbDisplayName, size){if(window.openDatabase)this.db = openDatabase(dbName, version, dbDisplayName, size);}, exe: function(sql, args, callback){if(!this.db){X.log('Web sql not support!');return;}this.db.transaction(function(tx){if(!sql.contains('t_key_val'))X.log('Web sql exe : ' + sql + ' || ' + (args ? args.join(',') : 'null'));tx.executeSql(sql, args, function(tx, results){if(callback)callback(results);}, function(tx, err){// SQLErrorX.log('Web sql execute error: ' + err.message);});});},exeSqlLl: function(sqlLl, pre, suf){if(!this.db){X.log('Web sql not support!');return;}pre = pre || '';suf = suf || '';this.db.transaction(function(tx){X.log('Web sql exe : ' + sqlLl.length);var savedLog = false;var i = 0;for (; i < sqlLl.length; i++){var sql = sqlLl[i];if(sql.trim()){sql = pre + sql + suf;tx.executeSql(sql, null, null, function(tx, err){// SQLErrorX.log('Web sql execute error: ' + err.message);if(!savedLog){X.logDb('Web sql execute error: ' + err.message);X.logDb('Web sql sql: ' + sql);savedLog = true;}});}}});},trans: function(fn){if(!this.db){X.log('Web sql not support!');return;}this.db.transaction(fn);}, // crudadd: function(data, table){var keys = _.keys(data);var str1 = keys.join(',');var str2 = _.map(keys, function(it){return '?';}).join(',');var sql = 'insert into {0} ({1}) values ({2})';sql = sql.format(table, str1, str2);var args = _.values(data);this.exe(sql, args)}, del: function(data, table){var keys = _.keys(data);var strClause = _.map(keys, function(it){return it + ' = ?';}).join(' and ');var sql = 'delete from {0} where {1}';sql = sql.format(table, strClause);var args = _.values(data);this.exe(sql, args)}, update: function(data, dataClause, table){var strSet = _.map(_.keys(data), function(it){return it + ' = ?';}).join(', ');var argsSet = _.values(data);var strClause = _.map(_.keys(dataClause), function(it){return it + ' = ?';}).join(' and ');var argsClause = _.values(dataClause);var sql = 'update {0} set {1} where {2}';sql = sql.format(table, strSet, strClause);this.exe(sql, argsSet.merge(argsClause))}, queryItem: function(sql, args, callback){this.exe(sql, args, function(results){if(callback){if(results.rows.length > 0){var item = results.rows.item(0);if(!sql.contains('t_key_val'))X.log('Query resultset item : ' + JSON.stringify(item));callback(item);}else{callback(null);}}});}, query: function(sql, args, callback){this.exe(sql, args, function(results){X.log('Query resultset size : ' + results.rows.length);if(callback)callback(results.rows);});}, queryAndMap: function(sql, args, callback, callback2){this.query(sql, args, function(rows){if(callback){var i = 0;for (; i < rows.length; i++){var record = rows.item(i);callback(record, i);}}if(callback2)callback2(rows);});}, pi: function(sql, args, cp, npp, callback){var pager = new XPager(cp, npp, 0);var countSql = 'select count(1) as rowCount from ({0})'.format(sql);var subSql = 'select * from ({0}) limit {1}, {2}'.format(sql, pager.getStart(), npp);var _this = this;this.query(countSql, args, function(rows){pager.rowCount = rows.item(0)['rowCount'];_this.query(subSql, args, function(rows){if(callback)callback(pager, rows);});});}, piAndMap: function(sql, args, cp, npp, callback, callback2){this.pi(sql, args, cp, npp, function(pager, rows){if(callback){var i = 0;for (; i < rows.length; i++){var record = rows.item(i);callback(record, i);}if(callback2)callback2(pager);}});}, dump : ''};// HTML5本地存储只能存字符串// 当本地存储受限时候，使用dbvar XLocal = {storage: null,keyGlobal: null, init: function(key){if(window.localStorage){this.storage = window.localStorage;if(key){this.keyGlobal = key;}}else{X.log('Web localStorage api not support!');}}, clear: function(){if(!this.storage){X.log('Web localStorage api not support!');return;}if(this.keyGlobal){this.storage.removeItem(this.keyGlobal);}else{this.storage.clear();}}, get: function(key, unpack){if(!this.storage){X.log('Web localStorage api not support!');return;}if(!this.keyGlobal){var str = this.storage[key];if(!str || 'undefined' == str || 'null' == str)return nullif(unpack)str = LzwCN.unpack(str);return JSON.parse(str);}else{var str = this.storage[this.keyGlobal];if(str){var item = JSON.parse(str);return item ? item[key] : null;}}}, put: function(key, val, pack){if(!this.storage){X.log('Web localStorage api not support!');return;}X.log('Web localStorage put ' + key);if(!this.keyGlobal){// 先删除，ipad localstorage不删除会有问题？// http://stackoverflow.com/questions/5887326/is-localstorage-reliable-on-an-ipadthis.remove(key);var str = JSON.stringify(val);if(pack)str = LzwCN.pack(str);this.storage[key] = str;}else{this.remove(key);var item = {};var str = this.storage[this.keyGlobal];if(str) item = JSON.parse(str);item[key] = val;this.storage[this.keyGlobal] = JSON.stringify(item);}},remove: function(key){if(!this.storage){X.log('Web localStorage api not support!');return;}X.log('Web localStorage remove ' + key);if(!this.keyGlobal){this.storage.removeItem(key);}else{var str = this.storage[this.keyGlobal];if(str){var item = JSON.parse(str);if(item){item[key] = null;this.storage[this.keyGlobal] = JSON.stringify(item);}}}}, dump: ''}; var XLocalDB = {init: function(){XDB.exe('create table if not exists t_key_val(k varchar,v varchar)');}, clear: function(){var sql = 'delete from t_key_val';setTimeout(function(){XDB.exe(sql);}, 100);}, /*XLocalDB.clear()XLocalDB.put('y', {a: 'xx'})XLocalDB.get('y', function(item){X.log(item);});*/get: function(key, fn){var sql = 'select v from t_key_val where k = ?';var sqlArgs = [key];XDB.queryItem(sql, sqlArgs, function(item){if(!item){if(fn)fn(null);}else{var src = item.v;if(src){src = LzwCN.unpack(src);var val = JSON.parse(src);if(fn)fn(val);}else{if(fn)fn(null);}}});}, put: function(key, val){X.log('Web DB put ' + key);var src = JSON.stringify(val);src = LzwCN.pack(src);var item = {k: key, v: src};setTimeout(function(){XDB.add(item, 't_key_val');}, 100);},remove: function(key){X.log('Web DB remove ' + key);var item = {k: key};setTimeout(function(){XDB.del(item, 't_key_val');}, 100);}, dump: ''};

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注意：调用XDB方法时候，加上setTimeout，这点算是个hack，在使用web sql之前，还想到一个思路是进行字符串压缩，效果也很好，压缩率在50%以上，js的压缩类，我也贴下：

var LzwCN = {};LzwCN.compress = function(text){var result = [];for(var n = 0; n < text.length; n++){var c = text.charCodeAt(n);if (c < 128){result.push(String.fromCharCode(c));}else if (c > 127 && c < 2048){result.push(String.fromCharCode((c >> 6) | 192));result.push(String.fromCharCode((c & 63) | 128));}else{result.push(String.fromCharCode((c >> 12) | 224));result.push(String.fromCharCode(((c >> 6) & 63) | 128));result.push(String.fromCharCode((c & 63) | 128));}}return result.join('');};LzwCN.decompress = function(text){var result = [];var i = 0, c1 = 0, c2 = 0, c3 = 0;while(i < text.length){c1 = text.charCodeAt(i);if (c1 < 128){result.push(String.fromCharCode(c1));i++;}else if (c1 > 191 && c1 < 224){c2 = text.charCodeAt(i + 1);result.push(String.fromCharCode(((c1 & 31) << 6) | (c2 & 63)));i += 2;}else{c2 = text.charCodeAt(i + 1);c3 = text.charCodeAt(i + 2);result.push(String.fromCharCode(((c1 & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63)));i += 3;}}return result.join('');};LzwCN.pack = function(str){var result = [];var rstr = this.compress(str);var i = 0, size = 0, xstr = '', chars = 256, dict = [];for(i = 0; i < chars; i++){dict[String(i)] = i;}var splitted = rstr.split('');var buffer = [];var current = '';for(i = 0; i <= splitted.length; i++){current = new String(splitted[i]);xstr = (buffer.length == 0) ? String(current.charCodeAt(0)) : (buffer.join('-') + '-' + String(current.charCodeAt(0)));if (dict[xstr] !== undefined){buffer.push(current.charCodeAt(0));}else{result.push(String.fromCharCode(dict[buffer.join('-')]));dict[xstr] = chars;chars++;buffer = [current.charCodeAt(0)];}}return result.join('');};LzwCN.unpack = function(str){var i, chars = 256, dict = [];for(i = 0; i < chars; i++){dict[i] = String.fromCharCode(i);}var original = new String(str);var splitted = original.split('');var buffer = '';var chain = '';var result = [];for(i = 0; i < splitted.length; i++){var code = original.charCodeAt(i);var current = dict[code];if(buffer == ''){buffer = current;result.push(current);}else{if(code <= 255){result.push(current);chain = buffer + current;dict[chars] = chain;chars++;buffer = current;}else{chain = dict[code];if(chain == null){chain = buffer + buffer.slice(0, 1);}result.push(chain);dict[chars] = buffer + chain.slice(0, 1);chars++;buffer = chain;}}}return this.decompress(result.join(''));};

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最后一句：苹果在ios设备上对html5的支持，我个人表示不信任。