关于javascript:Util-JS判断任意类型变量是否为空

// 判断任意类型变量是否为空export function isNull (val) {    // null or undefined    if (val === null || val === undefined) return true;    if (typeof val === 'string' && val.trim() === "") return true;    if (typeof val === 'boolean') return false;    if (typeof val === 'number') return !val;    if (val instanceof Error) return val.message === '';    switch (Object.prototype.toString.call(val)) {        // String or Array        case '[object String]':        case '[object Array]':            return !val.length;        // Map or Set or File        case '[object File]':        case '[object Map]':        case '[object Set]': {            return !val.size;        }        // Plain Object        case '[object Object]': {            return !Object.keys(val).length;        }    }    return false;}