Javascript 在HTML5 localStorage中存储对象
我想在HTML5Javascript 在HTML5 localStorage中存储对象,javascript,html,local-storage,Javascript,Html,Local Storage,我想在HTML5localStorage中存储一个JavaScript对象,但我的对象显然正在转换为字符串 我可以使用localStorage存储和检索基本JavaScript类型和数组,但对象似乎不起作用。应该吗 这是我的密码: var testObject = { 'one': 1, 'two': 2, 'three': 3 }; console.log('typeof testObject: ' + typeof testObject); console.log('testObject p
localStorage
中存储一个JavaScript对象,但我的对象显然正在转换为字符串
我可以使用localStorage
存储和检索基本JavaScript类型和数组,但对象似乎不起作用。应该吗
这是我的密码:
var testObject = { 'one': 1, 'two': 2, 'three': 3 };
console.log('typeof testObject: ' + typeof testObject);
console.log('testObject properties:');
for (var prop in testObject) {
console.log(' ' + prop + ': ' + testObject[prop]);
}
// Put the object into storage
localStorage.setItem('testObject', testObject);
// Retrieve the object from storage
var retrievedObject = localStorage.getItem('testObject');
console.log('typeof retrievedObject: ' + typeof retrievedObject);
console.log('Value of retrievedObject: ' + retrievedObject);
控制台输出为
testObject的类型:对象
testObject属性:
1:1
2:2
3:3
retrievedObject的类型:字符串
retrievedObject的值:[对象]
在我看来,setItem
方法在存储输入之前将其转换为字符串
我在Safari、Chrome和Firefox中看到了这种行为,所以我认为这是我对规范的误解,而不是特定于浏览器的错误或限制
我试图理解中描述的结构化克隆算法。我不完全理解它在说什么,但我的问题可能与我的对象的属性不可枚举有关(?)
有简单的解决方法吗
更新:W3C最终改变了对结构化克隆规范的想法,并决定更改规范以匹配实现。看见因此,这个问题不再是100%有效的,但答案可能仍然很有趣。查看文档和文档,该功能似乎仅限于处理字符串键/值对 解决方法可以是在存储对象之前对其进行解析,然后在检索对象时对其进行解析:
var testObject = { 'one': 1, 'two': 2, 'three': 3 };
// Put the object into storage
localStorage.setItem('testObject', JSON.stringify(testObject));
// Retrieve the object from storage
var retrievedObject = localStorage.getItem('testObject');
console.log('retrievedObject: ', JSON.parse(retrievedObject));
您可能会发现使用以下方便的方法扩展存储对象很有用:
Storage.prototype.setObject = function(key, value) {
this.setItem(key, JSON.stringify(value));
}
Storage.prototype.getObject = function(key) {
return JSON.parse(this.getItem(key));
}
通过这种方式,您可以获得真正想要的功能,即使在API下面只支持字符串。对:
因为,
getObject()
将立即返回null
,如果key
不在存储中。如果值
为”
(空字符串;JSON.parse()
无法处理该问题),它也不会引发语法错误
异常。扩展存储对象是一个很棒的解决方案。对于我的API,我已经为localStorage创建了一个facade,然后在设置和获取时检查它是否是对象
var data = {
set: function(key, value) {
if (!key || !value) {return;}
if (typeof value === "object") {
value = JSON.stringify(value);
}
localStorage.setItem(key, value);
},
get: function(key) {
var value = localStorage.getItem(key);
if (!value) {return;}
// assume it is an object that has been stringified
if (value[0] === "{") {
value = JSON.parse(value);
}
return value;
}
}
理论上,可以使用以下函数存储对象:
function store (a)
{
var c = {f: {}, d: {}};
for (var k in a)
{
if (a.hasOwnProperty(k) && typeof a[k] === 'function')
{
c.f[k] = encodeURIComponent(a[k]);
}
}
c.d = a;
var data = JSON.stringify(c);
window.localStorage.setItem('CODE', data);
}
function restore ()
{
var data = window.localStorage.getItem('CODE');
data = JSON.parse(data);
var b = data.d;
for (var k in data.f)
{
if (data.f.hasOwnProperty(k))
{
b[k] = eval("(" + decodeURIComponent(data.f[k]) + ")");
}
}
return b;
}
但是,函数序列化/反序列化是不可靠的,因为。有一个很棒的库,它封装了许多解决方案,因此它甚至支持名为 您可以设置一个对象
$.jStorage.set(key, value)
而且很容易找到它
value = $.jStorage.get(key)
value = $.jStorage.get(key, "default value")
我是在偶然发现另一篇文章后写这篇文章的,这篇文章已经作为这篇文章的副本关闭了,标题是“如何在localstorage中存储数组?”。这很好,只是这两个线程都没有提供关于如何在localStorage中维护阵列的完整答案——不过我已经根据这两个线程中包含的信息设计了一个解决方案 因此,如果其他任何人希望能够在一个数组中推送/弹出/移动项目,并且他们希望该数组存储在localStorage或sessionStorage中,那么您可以这样做:
Storage.prototype.getArray = function(arrayName) {
var thisArray = [];
var fetchArrayObject = this.getItem(arrayName);
if (typeof fetchArrayObject !== 'undefined') {
if (fetchArrayObject !== null) { thisArray = JSON.parse(fetchArrayObject); }
}
return thisArray;
}
Storage.prototype.pushArrayItem = function(arrayName,arrayItem) {
var existingArray = this.getArray(arrayName);
existingArray.push(arrayItem);
this.setItem(arrayName,JSON.stringify(existingArray));
}
Storage.prototype.popArrayItem = function(arrayName) {
var arrayItem = {};
var existingArray = this.getArray(arrayName);
if (existingArray.length > 0) {
arrayItem = existingArray.pop();
this.setItem(arrayName,JSON.stringify(existingArray));
}
return arrayItem;
}
Storage.prototype.shiftArrayItem = function(arrayName) {
var arrayItem = {};
var existingArray = this.getArray(arrayName);
if (existingArray.length > 0) {
arrayItem = existingArray.shift();
this.setItem(arrayName,JSON.stringify(existingArray));
}
return arrayItem;
}
Storage.prototype.unshiftArrayItem = function(arrayName,arrayItem) {
var existingArray = this.getArray(arrayName);
existingArray.unshift(arrayItem);
this.setItem(arrayName,JSON.stringify(existingArray));
}
Storage.prototype.deleteArray = function(arrayName) {
this.removeItem(arrayName);
}
示例用法-在localStorage阵列中存储简单字符串:
localStorage.pushArrayItem('myArray','item one');
localStorage.pushArrayItem('myArray','item two');
var item1 = {}; item1.name = 'fred'; item1.age = 48;
sessionStorage.pushArrayItem('myArray',item1);
var item2 = {}; item2.name = 'dave'; item2.age = 22;
sessionStorage.pushArrayItem('myArray',item2);
示例用法-将对象存储在会话存储阵列中:
localStorage.pushArrayItem('myArray','item one');
localStorage.pushArrayItem('myArray','item two');
var item1 = {}; item1.name = 'fred'; item1.age = 48;
sessionStorage.pushArrayItem('myArray',item1);
var item2 = {}; item2.name = 'dave'; item2.age = 22;
sessionStorage.pushArrayItem('myArray',item2);
操作数组的常用方法:
.pushArrayItem(arrayName,arrayItem); -> adds an element onto end of named array
.unshiftArrayItem(arrayName,arrayItem); -> adds an element onto front of named array
.popArrayItem(arrayName); -> removes & returns last array element
.shiftArrayItem(arrayName); -> removes & returns first array element
.getArray(arrayName); -> returns entire array
.deleteArray(arrayName); -> removes entire array from storage
是一个本地存储层,允许您编写以下内容:
var store = Rhaboo.persistent('Some name');
store.write('count', store.count ? store.count+1 : 1);
store.write('somethingfancy', {
one: ['man', 'went'],
2: 'mow',
went: [ 2, { mow: ['a', 'meadow' ] }, {} ]
});
store.somethingfancy.went[1].mow.write(1, 'lawn');
storage.data.list.push('more data');
storage.another.list.splice(1, 2, {another: 'object'});
它不使用JSON.stringify/parse,因为在大型对象上这样做不准确且速度慢。相反,每个终端值都有自己的localStorage条目
您可能会猜到我可能与rhaboo有关。Stringify并不能解决所有问题
这里的答案似乎没有涵盖JavaScript中可能的所有类型,因此这里有一些关于如何正确处理这些类型的简短示例:
//Objects and Arrays:
var obj = {key: "value"};
localStorage.object = JSON.stringify(obj); //Will ignore private members
obj = JSON.parse(localStorage.object);
//Boolean:
var bool = false;
localStorage.bool = bool;
bool = (localStorage.bool === "true");
//Numbers:
var num = 42;
localStorage.num = num;
num = +localStorage.num; //short for "num = parseFloat(localStorage.num);"
//Dates:
var date = Date.now();
localStorage.date = date;
date = new Date(parseInt(localStorage.date));
//Regular expressions:
var regex = /^No\.[\d]*$/i; //usage example: "No.42".match(regex);
localStorage.regex = regex;
var components = localStorage.regex.match("^/(.*)/([a-z]*)$");
regex = new RegExp(components[1], components[2]);
//Functions (not recommended):
function func(){}
localStorage.func = func;
eval( localStorage.func ); //recreates the function with the name "func"
我不建议存储函数,因为eval()
是邪恶的,会导致安全、优化和调试方面的问题。
一般来说,eval()
不应在JavaScript代码中使用
私人成员
使用JSON.stringify()
存储对象的问题是,此函数无法序列化私有成员。
这个问题可以通过覆盖.toString()
方法(在web存储中存储数据时隐式调用)来解决:
循环引用
另一个stringify
无法解决的问题是循环引用:
var obj = {};
obj["circular"] = obj;
localStorage.object = JSON.stringify(obj); //Fails
在本例中,JSON.stringify()
将抛出一个TypeError
“将循环结构转换为JSON”。
如果应该支持存储循环引用,则可以使用JSON.stringify()
的第二个参数:
var obj = {id: 1, sub: {}};
obj.sub["circular"] = obj;
localStorage.object = JSON.stringify( obj, function( key, value) {
if( key == 'circular') {
return "$ref"+value.id+"$";
} else {
return value;
}
});
然而,找到存储循环引用的有效解决方案在很大程度上取决于需要解决的任务,恢复此类数据也不是一件小事
关于如何处理这个问题,已经存在一些问题:这里是@danott发布的代码的一些扩展版本 它还将实现从本地存储中删除值 并演示如何添加Getter和Setter层,以便
localstorage.setItem(预览,true)
你可以写
config.preview=true
好了,我们走吧:
var PT=Storage.prototype
if (typeof PT._setItem >='u') PT._setItem = PT.setItem;
PT.setItem = function(key, value)
{
if (typeof value >='u')//..ndefined
this.removeItem(key)
else
this._setItem(key, JSON.stringify(value));
}
if (typeof PT._getItem >='u') PT._getItem = PT.getItem;
PT.getItem = function(key)
{
var ItemData = this._getItem(key)
try
{
return JSON.parse(ItemData);
}
catch(e)
{
return ItemData;
}
}
// Aliases for localStorage.set/getItem
get = localStorage.getItem.bind(localStorage)
set = localStorage.setItem.bind(localStorage)
// Create ConfigWrapperObject
var config = {}
// Helper to create getter & setter
function configCreate(PropToAdd){
Object.defineProperty( config, PropToAdd, {
get: function () { return ( get(PropToAdd) ) },
set: function (val) { set(PropToAdd, val ) }
})
}
//------------------------------
// Usage Part
// Create properties
configCreate('preview')
configCreate('notification')
//...
// Config Data transfer
//set
config.preview = true
//get
config.preview
// delete
config.preview = undefined
您可以使用
.bind(…)
剥离别名部分。不过我只是把它放进去了,因为知道这件事真的很好。我花了几个小时才弄明白为什么一个简单的get=localStorage.getItem代码>不工作建议对此处讨论的许多功能使用抽象库,并提供更好的兼容性。有很多选择:
- 或者我做了一个东西,它不会破坏现有的存储对象,而是创建了一个包装器,这样您就可以随心所欲了。结果是一个普通对象,没有方法,具有与任何对象一样的访问权限
如果希望1
localStorage
属性具有魔力:
var prop = ObjectStorage(localStorage, 'prop');
如果您需要几个:
var storage = ObjectStorage(localStorage, ['prop', 'more', 'props']);
一切
{
"d": {"$date": 1358205756553},
"b": {"$binary": "c3VyZS4="}
}
localStorage.set('myKey',{a:[1,2,5], b: 'ok'});
localStorage.has('myKey'); // --> true
localStorage.get('myKey'); // --> {a:[1,2,5], b: 'ok'}
localStorage.keys(); // --> ['myKey']
localStorage.remove('myKey');
localDataStorage.set( 'key1', 'Belgian' )
localDataStorage.set( 'key2', 1200.0047 )
localDataStorage.set( 'key3', true )
localDataStorage.set( 'key4', { 'RSK' : [1,'3',5,'7',9] } )
localDataStorage.set( 'key5', null )
localDataStorage.get( 'key1' ) --> 'Belgian'
localDataStorage.get( 'key2' ) --> 1200.0047
localDataStorage.get( 'key3' ) --> true
localDataStorage.get( 'key4' ) --> Object {RSK: Array(5)}
localDataStorage.get( 'key5' ) --> null
/**
* Silly wrapper to be able to type the storage keys
*/
export class TypedStorage<T> {
public removeItem(key: keyof T): void {
localStorage.removeItem(key);
}
public getItem<K extends keyof T>(key: K): T[K] | null {
const data: string | null = localStorage.getItem(key);
return JSON.parse(data);
}
public setItem<K extends keyof T>(key: K, value: T[K]): void {
const data: string = JSON.stringify(value);
localStorage.setItem(key, data);
}
}
// write an interface for the storage
interface MyStore {
age: number,
name: string,
address: {city:string}
}
const storage: TypedStorage<MyStore> = new TypedStorage<MyStore>();
storage.setItem("wrong key", ""); // error unknown key
storage.setItem("age", "hello"); // error, age should be number
storage.setItem("address", {city:"Here"}); // ok
const address: {city:string} = storage.getItem("address");
obj = {
L: {
L: { v: 'lorem' },
R: { v: 'ipsum' }
},
R: {
L: { v: 'dolor' },
R: {
L: { v: 'sit' },
R: { v: 'amet' }
}
}
}
obj.R.L.uncle = obj.L;
obj.R.R.uncle = obj.L;
obj.R.R.L.uncle = obj.R.L;
obj.R.R.R.uncle = obj.R.L;
obj.L.L.uncle = obj.R;
obj.L.R.uncle = obj.R;
LOCALSTORAGE.setObject('latinUncles', obj)
recovered = LOCALSTORAGE.getObject('latinUncles')
[
obj.L.L.v === recovered.L.L.v,
obj.L.R.v === recovered.L.R.v,
obj.R.L.v === recovered.R.L.v,
obj.R.R.L.v === recovered.R.R.L.v,
obj.R.R.R.v === recovered.R.R.R.v,
obj.R.L.uncle === obj.L,
obj.R.R.uncle === obj.L,
obj.R.R.L.uncle === obj.R.L,
obj.R.R.R.uncle === obj.R.L,
obj.L.L.uncle === obj.R,
obj.L.R.uncle === obj.R,
recovered.R.L.uncle === recovered.L,
recovered.R.R.uncle === recovered.L,
recovered.R.R.L.uncle === recovered.R.L,
recovered.R.R.R.uncle === recovered.R.L,
recovered.L.L.uncle === recovered.R,
recovered.L.R.uncle === recovered.R
]
var myObj = [{name:"test", time:"Date 2017-02-03T08:38:04.449Z"}];
localStorage.setItem('item', JSON.stringify(myObj));
var getObj = JSON.parse(localStorage.getItem('item'));
localStorage.setItem('user', JSON.stringify(user));
var user = JSON.parse(localStorage.getItem('user'));
If we need to delete all entries of the store we can simply do:
localStorage.clear();
const objectMapper = new ObjectMapper();
localstore.setItem(key, objectMapper.stringify<yourObjectType>(yourObject));
Storage.prototype.setObject = function (key: string, value: unknown) {
this.setItem(key, JSON.stringify(value));
};
Storage.prototype.getObject = function (key: string) {
const value = this.getItem(key);
if (!value) {
return null;
}
return JSON.parse(value);
};
declare global {
interface Storage {
setObject: (key: string, value: unknown) => void;
getObject: (key: string) => unknown;
}
}
localStorage.setObject('ages', [23, 18, 33, 22, 58]);
localStorage.getObject('ages');