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

我正在做以下事情:

getLocalStorageSizeLimit = function () {

    var maxLength = Math.pow(2,24);
    var preLength = 0;
    var hugeString = "0";
    var testString;
    var keyName = "testingLengthKey";

    //2^24 = 16777216 should be enough to all browsers
    testString = (new Array(Math.pow(2, 24))).join("X");

    while (maxLength !== preLength) {
        try  {
            localStorage.setItem(keyName, testString);

            preLength = testString.length;
            maxLength = Math.ceil(preLength + ((hugeString.length - preLength) / 2));

            testString = hugeString.substr(0, maxLength);
        } catch (e) {
            hugeString = testString;

            maxLength = Math.floor(testString.length - (testString.length - preLength) / 2);
            testString = hugeString.substr(0, maxLength);
        }
    }

    localStorage.removeItem(keyName);

    // Original used this.storageObject in place of localStorage.  I can only guess the goal is to check the size of the localStorage with everything but the testString given that maxLength is then added.
    maxLength = JSON.stringify(localStorage).length + maxLength + keyName.length - 2;

    return maxLength;
};

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。

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

我将二进制测试压缩到我使用的这个函数中:

function getStorageTotalSize(upperLimit/*in bytes*/) {
    var store = localStorage, testkey = "$_test"; // (NOTE: Test key is part of the storage!!! It should also be an even number of characters)
    var test = function (_size) { try { store.removeItem(testkey); store.setItem(testkey, new Array(_size + 1).join('0')); } catch (_ex) { return false; } return true; }
    var backup = {};
    for (var i = 0, n = store.length; i < n; ++i) backup[store.key(i)] = store.getItem(store.key(i));
    store.clear(); // (you could iterate over the items and backup first then restore later)
    var low = 0, high = 1, _upperLimit = (upperLimit || 1024 * 1024 * 1024) / 2, upperTest = true;
    while ((upperTest = test(high)) && high < _upperLimit) { low = high; high *= 2; }
    if (!upperTest) {
        var half = ~~((high - low + 1) / 2); // (~~ is a faster Math.floor())
        high -= half;
        while (half > 0) high += (half = ~~(half / 2)) * (test(high) ? 1 : -1);
        high = testkey.length + high;
    }
    if (high > _upperLimit) high = _upperLimit;
    store.removeItem(testkey);
    for (var p in backup) store.setItem(p, backup[p]);
    return high * 2; // (*2 because of Unicode storage)
}

它还在测试之前备份内容，然后恢复它们。

它的工作原理:它将大小增加一倍，直到达到限制或测试失败。然后它存储低和高之间的距离的一半，并每次减去/增加一半(失败时减去，成功时增加);磨炼成合适的值。

默认情况下，upperLimit为1GB，仅限制在开始二分查找之前以指数方式向上扫描的距离。我怀疑这种情况是否需要改变，但我总是未雨绸缪。；）

铬:

> getStorageTotalSize();
> 10485762
> 10485762/2
> 5242881
> localStorage.setItem("a", new Array(5242880).join("0")) // works
> localStorage.setItem("a", new Array(5242881).join("0")) // fails ('a' takes one spot [2 bytes])

IE11、Edge和FireFox也报告了相同的最大大小(10485762字节)。

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。