html5 localstorage能存多少数据

根据 WHATWG 规范描述如下：

A mostly arbitrary limit of five megabytes per origin is recommended. Implementation feedback is welcome and will be used to update this suggestion in the future.

规范建议的本地数据存储不超过5M,同时大多数浏览器默认的localstorage存储大小也是5M限制。

localstorage大小限制可以通过以下面的代码进行测试：

var allocated = 5;
var total = 0;
for(var x in localStorage){  
    var amount = (localStorage[x].length * 2) / 1024 / 1024;  
    total += amount;  
}
var remaining = allocated - total;
console.log( "Used: " + total + " MB");
console.log( "Remaining: " + remaining + " MB");

需要在localstorage中存储超过5M的数据时可以通过下面的方法来实现：

// 1. 将下面一行文件复制到你的文件中
!function(){function e(t,o){return n?void(n.transaction("s").objectStore("s").get(t).onsuccess=function(e){var t=e.target.result&&e.target.result.v||null;o(t)}):void setTimeout(function(){e(t,o)},100)}var t=window.indexedDB||window.mozIndexedDB||window.webkitIndexedDB||window.msIndexedDB;if(!t)return void console.error("indexDB not supported");var n,o={k:"",v:""},r=t.open("d2",1);r.onsuccess=function(e){n=this.result},r.onerror=function(e){console.error("indexedDB request error"),console.log(e)},r.onupgradeneeded=function(e){n=null;var t=e.target.result.createObjectStore("s",{keyPath:"k"});t.transaction.oncomplete=function(e){n=e.target.db}},window.ldb={get:e,set:function(e,t){o.k=e,o.v=t,n.transaction("s","readwrite").objectStore("s").put(o)}}}();

// 2. 存储值
ldb.set('nameGoesHere', 'value goes here');

// 3. 获取值
ldb.get('nameGoesHere', function (value) {
  console.log('And the value is', value);
});

参考：https://github.com/DVLP/localStorageDB