精确到小数点后两位并自动补0

export const nub= (num) => {
     let f_x=parseFloat(num)
       if(isNaN(f_x)){
         return false
       }
        let ff=Math.round(num*100)/100
        let s_x=ff.toString()
        let pos=s_x.indexOf(".")
         if(pos<0){
           pos=s_x.length
           s_x+="."
         }
        while(s_x.length<=pos+2){
           s_x+="0"
        }
       return s_x
};