JS - type judgment

/* 字符串 */
export function isString(arg) {
    
    
    return Object.prototype.toString.call(arg) == "[object String]";
}
/* 数字 */
export function isNumber(arg) {
    
    
    return Object.prototype.toString.call(arg) == "[object Number]";
}
/* 布尔 */
export function isBoolean(arg) {
    
    
    return Object.prototype.toString.call(arg) == "[object Boolean]";
}
/* 数组 */
export function isArray(arg) {
    
    
    return Object.prototype.toString.call(arg) == "[object Array]";
}
/* 对象 */
export function isObject(arg) {
    
    
    return Object.prototype.toString.call(arg) == '[object Object]';
}
/* 函数 */
export function isFunction(arg) {
    
    
    return Object.prototype.toString.call(arg) == '[object Function]';
}
/* 是否为空 */
export function isEmpty(arg) {
    
    
  if (arg === undefined || arg === null || arg != arg) {
    
    
    return true
  }
  let arg_ = arg.toString()
  return Object.keys(arg_).length === 0;
}