javascript 如何增加 localStorage 的值
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How to increment a value at localStorage
提问by Sana Joseph
I have some values that are dynamically stored at localStorage with incremented values like this: localStorage["Value0"], localStorage["Value1"],....
我有一些动态存储在 localStorage 中的值，这些值具有如下递增值：localStorage["Value0"], localStorage["Value1"],....
When I try to access them like this:
当我尝试像这样访问它们时：
JavaScript:
JavaScript：
localStorage["Counter"]=0;
var i = localStorage["Counter"];
var d =localStorage["Value"+i];
i = i + 1; // i becomes "01"
var f = localStorage["Value"+i];
The i's value is "01" not 1 ... Is there a way to increment the i's value correctly?
i 的值是“01”而不是 1 ......有没有办法正确增加 i 的值？
回答by Wern Ancheta
LocalStorage can only store string values. You can use parseInt which converts a string into an integer:
LocalStorage 只能存储字符串值。您可以使用 parseInt 将字符串转换为整数：
var new_value = parseInt(localStorage.getItem('num')) + 1
You can also use libraries like store.js to do things automatically for you. All you have to do is to include the library:
您还可以使用 store.js 之类的库来自动为您做事。您所要做的就是包含库：
<script src="store.js"></script>
Set a new storage:
设置一个新的存储：
var numbers = new Store("numbers")
Put things into it:
把东西放进去：
numbers.set('num', 2)
Get the value and do anything you want with it:
获取价值并用它做任何你想做的事：
numbers.get('num') + 1 //output: 3
And you can also go crazy and use some arrays:
你也可以疯狂使用一些数组：
numbers.set('nums', [1,2,3])
And change things inside it:
并改变里面的东西：
numbers.get('nums')[0] + 3 //output: 4
No type conversion needed. You can also store objects, booleans and other stuff. Just don't forget to save things back in the storage since it doesn't automatically do it.
不需要类型转换。您还可以存储对象、布尔值和其他东西。只是不要忘记将内容保存回存储中，因为它不会自动执行此操作。
回答by Rob W
To fix the problem of getting 01, simply convert the variable to a number:
要解决 get 的问题01，只需将变量转换为数字：
var i = +localStorage.getItem('Counter'); // or +localStorage.Counter;
If you want an incremental key name, the following code can also be used (provided that you don't delete keys in between):
如果你想要一个增量键名，也可以使用下面的代码（前提是你不要删除中间的键）：
var keyname = 'Value' + localStorage.length;
localstorage.setItem(keyname, value);
