详解怎样获得localStorage最大储存尺寸的方式

(function() {
    if(!window.localStorage) {
        console.log('当今访问器不适用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超过最大限定');
            clearInterval(show);
        }
    }, 0.1)
})()