input 限制只能输入数字，且保留小数后两位

 <input  @keyup="getNumber($event)" v-model="balance_amount"  placeholder="请输入余额"/>

getNumber(e){
   let value = e.target.value;
   let num = value.match(/\d+(\.\d{0,2})?/)? value.match(/\d+(\.\d{0,2})?/)[0]: '';
   this.balance_amount = num;
},