捕获存储异常

try {
    localStorage.setItem(key, value);
} catch (oException) {
    if (oException.name === 'QuotaExceededError') {
        console.log('超出本地存储限额！');
        // 清空后，再设置
        localStorage.clear();
        localStorage.setItem(key, value);
    }
}

获取存储大小限制

(function() {
    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)
}
)()

获取当前存储的size

// 示例代码
function get_cache_size(t) {
    t = t == undefined ? "l" : t;
    var obj = "";
    if (t === 'l') {
        if (!window.localStorage) {
            console.log('浏览器不支持localStorage');
        } else {
            obj = window.localStorage;
        }
    } else {
        if (!window.sessionStorage) {
            console.log('浏览器不支持sessionStorage');
        } else {
            obj = window.sessionStorage;
        }
    }
    if (obj !== "") {
        var size = 0;
        for (item in obj) {
            if (obj.hasOwnProperty(item)) {
                size += obj.getItem(item).length;
            }
        }
        console.log('当前已用存储：' + (size / 1024).toFixed(2) + 'KB');
    }
}
get_cache_size('l'); //localStorage当前大小
get_cache_size('s'); //sessionStorage当前大小