【转】HTML5 本地存储五种方案

时间:2024-06-25 20:35:08

1、LocalStorage

LocalStorage就是Key-Value的简单键值对存储结构,Web Storage除了localStorage的持久性存储外,还

有针对本次回话的sessionStorage方式,一般情况下localStorage较为常用,示例代码如下:

Chrome中 的存储方式是以sqlite的数据库文件形式存储。存在C:\Users\Username\AppData\Local

\Google\Chrome\User Data\Default\Local Storage 中

function save(dataModel){

var value = dataModel.serialize();

window.localStorage['DataModel'] = value;

window.localStorage['DataCount'] = dataModel.size();

console.log(dataModel.size() + ' datas are saved');

return value;

}

function restore(dataModel){

var value = window.localStorage['DataModel'];

if(value){

dataModel.deserialize(value);

console.log(window.localStorage['DataCount'] + ' datas are restored');

return value;

}

return '';

}

function clear(){

if(window.localStorage['DataModel']){

console.log(window.localStorage['DataCount'] + ' datas are cleared');

delete window.localStorage['DataModel'];

delete window.localStorage['DataCount'];

}

}



2、Cookie


这种存储方式存储内容很有限,只适合做简单信息存储,存取接口设计得极其反人类,举例如下:

function getCookieValue(name) {

if (document.cookie.length > 0) {

var start = document.cookie.indexOf(name + "=");

if (start !== -1) {

start = start + name.length + 1;

var end = document.cookie.indexOf(";", start);

if (end === -1){

end = document.cookie.length;

}

return unescape(document.cookie.substring(start, end));

}

}

return '';

}

function save(dataModel) {

var value = dataModel.serialize();

document.cookie = 'DataModel=' + escape(value);

document.cookie = 'DataCount=' + dataModel.size();

console.log(dataModel.size() + ' datas are saved');

return value;

}

3、Indexed Database API



IndexedDB可以存储结构对象,可构建key和index的索引方式查找,目前各浏览器的已经逐渐支持

IndexedDB的存储方式,其使用代码如下,需注意IndexedDB的很多操作接口类似NodeJS的异步回调方式,

特别是查询时连cursor的continue都是异步再次回调onsuccess函数的操作方式,因此和NodeJS一样使用上不如同步的代码容易。

function save(dataModel){

var tx = db.transaction("meters", "readwrite");

var store = tx.objectStore("meters");

dataModel.each(function(data){

store.put({

id: data.getId(),

tag: data.getTag(),

name: data.getName(),

meterValue: data.a('meter.value'),

meterAngle: data.a('meter.angle'),

p3: data.p3(),

r3: data.r3(),

s3: data.s3()

});

});

tx.oncomplete = function() {

console.log(dataModel.size() + ' datas are saved');

};

return dataModel.serialize();

}

4、FileSystem API



FileSystem API相当于操作本地文件的存储方式,目前支持浏览器不多,其接口标准也在发展制定变化中

,因此也可以动态生成图片到本地文件,然后通过 filesystem:http:*** 的URL方式直接赋值给img的

html元素的src访问。

function save(dataModel) {

var value = dataModel.serialize();

fs.root.getFile('meters.txt', {create: true}, function (fileEntry) {

console.log(fileEntry.toURL());

fileEntry.createWriter(function (fileWriter) {

fileWriter.onwriteend = function () {

console.log(dataModel.size() + ' datas are saved');

};

var blob = new Blob([value], {type: 'text/plain'});

fileWriter.write(blob);

});

});

return value;

}

5、Application Cache



window.applicationCache 对象是对浏览器的应用缓存的编程访问方式。其 status 属性可用于查看缓存的当前状态:

var appCache = window.applicationCache;

switch (appCache.status) {

case appCache.UNCACHED: // UNCACHED == 0

return 'UNCACHED';

break;

case appCache.IDLE: // IDLE == 1

return 'IDLE';

break;

case appCache.CHECKING: // CHECKING == 2

return 'CHECKING';

break;

case appCache.DOWNLOADING: // DOWNLOADING == 3

return 'DOWNLOADING';

break;

case appCache.UPDATEREADY: // UPDATEREADY == 4

return 'UPDATEREADY';

break;

case appCache.OBSOLETE: // OBSOLETE == 5

return 'OBSOLETE';

break;

default:

return 'UKNOWN CACHE STATUS';

break;

};