try_it() {
                try {
                    console.log(add("1",2))
                }catch(e){
                    console.log(e.name + ‘:‘ + e.message)
                }

            },
            add(a,b) {
                if(typeof a != "number" || typeof b != "number"){
                    throw{
                        name:‘typeErr‘,
                        message:‘you should enter a number‘
                    }
                }
                return a+b
            }
　　　　　　　try_it()