我真的很喜欢cdmckay的答案，但它并不真的看起来很好，实时检查大小:它太慢了(对我来说2秒)。这是改进的版本，它更快，更准确，也有一个选项来选择误差的大小(默认为250000，误差越小-计算时间越长):

function getLocalStorageMaxSize(error) {
  if (localStorage) {
    var max = 10 * 1024 * 1024,
        i = 64,
        string1024 = '',
        string = '',
        // generate a random key
        testKey = 'size-test-' + Math.random().toString(),
        minimalFound = 0,
        error = error || 25e4;

    // fill a string with 1024 symbols / bytes    
    while (i--) string1024 += 1e16;

    i = max / 1024;

    // fill a string with 'max' amount of symbols / bytes    
    while (i--) string += string1024;

    i = max;

    // binary search implementation
    while (i > 1) {
      try {
        localStorage.setItem(testKey, string.substr(0, i));
        localStorage.removeItem(testKey);

        if (minimalFound < i - error) {
          minimalFound = i;
          i = i * 1.5;
        }
        else break;
      } catch (e) {
        localStorage.removeItem(testKey);
        i = minimalFound + (i - minimalFound) / 2;
      }
    }

    return minimalFound;
  }
}

测试:

console.log(getLocalStorageMaxSize()); // takes .3s
console.log(getLocalStorageMaxSize(.1)); // takes 2s, but way more exact

对于标准错误，这工作得快得多;而且，在必要的时候，它可以更加精确。

引用维基百科关于Web存储的文章:

Web存储可以简单地看作是对cookie的改进，提供了更大的存储容量(在谷歌Chrome(https://plus.google.com/u/0/+FrancoisBeaufort/posts/S5Q9HqDB8bh)、Mozilla Firefox和Opera中，每个源的存储容量为10mb;在Internet Explorer中，每个存储区域为10mb)和更好的编程接口。

我还引用了John Resig在2007年1月发表的一篇文章:

Storage Space It is implied that, with DOM Storage, you have considerably more storage space than the typical user agent limitations imposed upon Cookies. However, the amount that is provided is not defined in the specification, nor is it meaningfully broadcast by the user agent. If you look at the Mozilla source code we can see that 5120KB is the default storage size for an entire domain. This gives you considerably more space to work with than a typical 2KB cookie. However, the size of this storage area can be customized by the user (so a 5MB storage area is not guaranteed, nor is it implied) and the user agent (Opera, for example, may only provide 3MB - but only time will tell.)

我真的很喜欢cdmckay的答案，但它并不真的看起来很好，实时检查大小:它太慢了(对我来说2秒)。这是改进的版本，它更快，更准确，也有一个选项来选择误差的大小(默认为250000，误差越小-计算时间越长):

function getLocalStorageMaxSize(error) {
  if (localStorage) {
    var max = 10 * 1024 * 1024,
        i = 64,
        string1024 = '',
        string = '',
        // generate a random key
        testKey = 'size-test-' + Math.random().toString(),
        minimalFound = 0,
        error = error || 25e4;

    // fill a string with 1024 symbols / bytes    
    while (i--) string1024 += 1e16;

    i = max / 1024;

    // fill a string with 'max' amount of symbols / bytes    
    while (i--) string += string1024;

    i = max;

    // binary search implementation
    while (i > 1) {
      try {
        localStorage.setItem(testKey, string.substr(0, i));
        localStorage.removeItem(testKey);

        if (minimalFound < i - error) {
          minimalFound = i;
          i = i * 1.5;
        }
        else break;
      } catch (e) {
        localStorage.removeItem(testKey);
        i = minimalFound + (i - minimalFound) / 2;
      }
    }

    return minimalFound;
  }
}

测试:

console.log(getLocalStorageMaxSize()); // takes .3s
console.log(getLocalStorageMaxSize(.1)); // takes 2s, but way more exact

对于标准错误，这工作得快得多;而且，在必要的时候，它可以更加精确。

你可以在现代浏览器中使用下面的代码来实时有效地检查存储配额(总量和使用):

if ('storage' in navigator && 'estimate' in navigator.storage) {
        navigator.storage.estimate()
            .then(estimate => {
                console.log("Usage (in Bytes): ", estimate.usage,
                            ",  Total Quota (in Bytes): ", estimate.quota);
            });
}

我编写了这段简单的代码，以字节为单位测试localStorage的大小。

https://github.com/gkucmierz/Test-of-localStorage-limits-quota

const check = bytes => {
  try {
    localStorage.clear();
    localStorage.setItem('a', '0'.repeat(bytes));
    localStorage.clear();
    return true;
  } catch(e) {
    localStorage.clear();
    return false;
  }
};

Github页面:

https://gkucmierz.github.io/Test-of-localStorage-limits-quota/

我在桌面谷歌chrome, opera, firefox, brave和移动chrome上有相同的结果，这是~10Mbytes

和一半小的结果safari约4mb

实际上Opera没有5MB的限制。它提供了增加限制的应用程序需要更多。用户甚至可以为一个域选择“无限存储”。

您可以自己轻松地测试localStorage限制/配额。