在localStorage中设置的字符串作为对象获取 [英] String set in localStorage gets as object

问题描述

我已经将JSON.stringified对象保存在localStorage中，但是将它们作为无法解析的对象("[object Object]")进行检索.

I've JSON.stringified objects to save in localStorage, but they're retrieved as objects ( "[object Object]" ) that can't be parsed.

场景:

我要做的第一件事是

localStorage.clear();

我创建了3个对象作为默认加载到localStorage中.每个对象都是JSON.stringified并使用其自己的密钥保存在localStorage中.然后，我使用一个for循环和localStorage.key(i)来获取密钥并检索对象(字符串).

I've created 3 objects to load into localStorage as a default. Each object is JSON.stringified and saved with it's own key in localStorage. Then, I use a for loop and localStorage.key(i) to get the key and retrieve the objects (strings).

if (localStorage.length === 0) {

// make 3 objects

console.log(typeof c);        // logs "string"
localStorage.setItem("_fruit", a);
localStorage.setItem("_veggie", b);
localStorage.setItem("_protein", c);
var test = localStorage.key(0);
test = localStorage.getItem(test);
console.log(test);           // logs stringified JSON
}

到目前为止，一切都很好.在if语句之外，我有:

So far so good. Outside the if statement I have:

var test = localStorage.key(0);
console.log(test);          // logs correct key
test = localStorage.getItem(test);
console.log(test);          // logs string of object
test = JSON.parse(test);
console.log(test);          // logs object correctly

这也输出到DOM罚款.但是一旦我注释掉

And this also outputs to the DOM fine. But as soon as I comment out

// localStorage.clear();

要测试从本地存储的检索，我遇到了这个问题:

To test the retrieval from local storage, I have this problem:

var test = localStorage.key(0);
console.log(test);          // logs correct key
test = localStorage.getItem(test);
console.log(test);          // logs "[object Object]"
test = JSON.parse(test);    <------ logs Unexpected token o in JSON at position 1
console.log(test);          // code stops above

我知道不能保证索引本地存储的顺序，这很好.如果可以，请使用React.

I'm aware there's no guarantee about the order of indexing local storage and that's fine. Using React if that makes a difference.

推荐答案

在存储对象之前，您需要对它进行字符串化:

You need to stringify an object before storing it:

localStorage.setItem('key', JSON.stringify(obj));

然后，在检索它时，您只需

Then, when retrieving it, you just do

JSON.parse(localStorage.getItem('key'));

之所以这样做是因为所有内容都存储为字符串，因此它调用.toString()方法，该方法对于对象返回[object Object]

The reason for this is that everything is stored as a string, so it calls the .toString() method, which for objects returns [object Object]

编辑 我注意到您说您确实对对象进行了字符串化.我猜想那将取决于对象的格式，但是我没有遇到任何不事先清除存储空间的问题.

EDIT I noticed you said you did stringify the objects. I guess it would depend the format of the object then, but I haven't encountered any issue with not clearing storage beforehand.

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