1. //使用循环语句来批量注册这些isType函数
    2. let utils = {}
    3. let types = ['String','Array','Number']
    4. types.forEach(type=>{
    5.     utils['is'+type] = function(obj){
    6.         return Object.prototype.toString.call(obj) === `[object ${type}]`
    7.     }
    8. })
    10. console.log(utils)
    11. console.log(utils.isArray([]))
    12. console.log(utils.isString("123"))