首先，一些有用的资源:

Firstly, some useful resources:

• 网络存储支持测试 - 有一个比较数据存储配额的表格浏览器之间.
• 简单localStorage 配额测试
• localStorage 浏览器行为摘要
• W3C 规范 - 指示用户代理(例如浏览器)的行为方式(localStorage 和 sessionStorage).

• Web Storage Support Test - has a table comparing data storage quotas between browsers.
• Simple localStorage quota test
• Summary of localStorage browser behaviour
• W3C spec - indicating how a user agent (e.g. browser) should behave (both localStorage and sessionStorage).

在回答您的问题时，桌面浏览器的初始最大 localStorage 配额往往为每个域 5MB.在某些情况下，这可以由用户进行调整:

In answer to your question, desktop browsers tend to have an initial maximum localStorage quota of 5MB per domain. This can be adjusted by the user in some cases:

• Opera:opera:config -> localStorage 的域配额
• Firefox:about:config -> dom.storage.default_quota

在 Chrome 中，用户似乎没有办法调整此设置，尽管与 Opera 一样，可以使用开发者工具直接按域编辑 localStorage 数据.

In Chrome, there doesn't seem to be a way for the user to adjust this setting although like Opera, localStorage data can be edited directly per domain using the Developer Tools.

当您尝试在 localStorage 中存储数据时，浏览器会检查当前域是否有足够的剩余空间.如果是:

When you try to store data in localStorage, the browser checks whether there's enough remaining space for the current domain. If yes:

• 存储数据，如果相同的键已存在，则覆盖值.

如果不是:

• 不会存储数据，也不会覆盖现有数据.
• 抛出一个 QUOTA_EXCEEDED_ERR 异常.

在这种情况下，getItem(key) 将返回最后成功存储的值(如果有).

In this case, getItem(key) will return the last value that was successfully stored, if any.

(Opera 略有不同，它显示一个对话框，让用户可以选择增加当前域的存储空间.)

(Opera is slightly different in that it displays a dialog box giving the user the choice of increasing storage space for the current domain.)

注意 sessionStorage 和 localStorage 都是同一个 Storage 对象的实现，所以它们的行为是相似的，错误处理是相同的.

Note that sessionStorage and localStorage are both implementations of the same Storage object so their behaviour is similar and error handling is the same.