场景：input框中默认存在value=0，输入时将0清空，当value=’ '时，恢复value=0

<van-field 
v-model="arr[0].value" 
name="stockInvest" 
type="digit"
maxlength="13" 
:formatter="zeroFormatter"
input-align="right"
label-width="50%"
@blur="onBlur(0)" />

 methods: {
    zeroFormatter (value) {
      if (value === '0' || value === '') {
        return value
      }
      return parseInt(value)
    },
    onBlur (i) {
      if (this.arr[i].value === '') {
        this.arr[i].value = 0
        return this.arr[i].value
      }
    }
  }```