由于localStorage(目前)只支持字符串作为值,为了做到这一点,对象需要在存储之前进行字符串化(存储为JSON-string),对于值的长度是否有定义的限制。
有人知道是否有一个适用于所有浏览器的定义吗?
由于localStorage(目前)只支持字符串作为值,为了做到这一点,对象需要在存储之前进行字符串化(存储为JSON-string),对于值的长度是否有定义的限制。
有人知道是否有一个适用于所有浏览器的定义吗?
当前回答
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)。
其他回答
不要认为5MB是可用的——local存储容量因浏览器而异,2.5MB、5MB和无限是最常见的值。 来源:http://dev-test.nemikor.com/web-storage/support-test/
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。
这里有一个简单的脚本来找出限制:
if (localStorage && !localStorage.getItem('size')) {
var i = 0;
try {
// Test up to 10 MB
for (i = 250; i <= 10000; i += 250) {
localStorage.setItem('test', new Array((i * 1024) + 1).join('a'));
}
} catch (e) {
localStorage.removeItem('test');
localStorage.setItem('size', i - 250);
}
}
这里是要点,JSFiddle和博客帖子。
该脚本将测试设置越来越大的文本字符串,直到浏览器抛出一个异常。这时,它将清除测试数据,并在localStorage中设置一个大小键,以千字节为单位存储大小。
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);
});
}