如何检测出Localstorage储存空间的大小

if (!window.localStorage) {

    console.log('当前浏览器不支持localStorage!')

}

var test = '0123456789';

var add = function (num) {

    num += num;

    if (num.length == 10240) {

        test = num;

        return;

    }

    add(num);

}

add(test);

var sum = test;

var show = setInterval(function () {

    sum += test;

    try {

        window.localStorage.removeItem('test');

        window.localStorage.setItem('test', sum);

        console.log(sum.length / 1024 + 'KB');

    } catch (e) {

        alert(sum.length / 1024 + 'KB超出最大限制');

        clearInterval(show);

    }

}, 0.1)