el-date-picker 开始时间选定后，结束时间不可选择开始时间之前的日期

<el-date-picker
            v-model="startTime"
            name="startTime"
            value-format="yyyy-MM-dd"
            type="date"
            @change="activityStartTime"
            placeholder="请选择开始日期"
            :picker-options="pickerOptions"
          />
<el-date-picker
            v-model="endTime"
            name="endTime"
            value-format="yyyy-MM-dd"
            type="date"
            @change="activityEndTime"
            placeholder="请选择结束日期"
            :picker-options="pickerOptions1"
          />

data(){
	return{
		startTime:new Date(new Date - 1000*60*60*24*31)，toLocaleDateString().split('/').map(item=>{if(item<10){return '0'+item}else{return item}}).join('-'),
		endTime:new Date().toLocaleDateString().split('/').map(item=>{if(item<10){return '0'+item}else{return item}}).join('-'),
		pickerOptions:{},
		pickerOptions1:{}
	}
}

activityStartTime(val){
	this.pickerOptions1 = Object.assign({}, this.pickerOptions,{
		disabledDate: time => {
			return (
				new Date(time).getTime() <= new Date(this.startTime)
			)
		}
	})
}

activityEndTime(val){
	if(!value){
		this.pickerOptions = Object.assign({}, this.pickerOptions1,{
			disabledDate: time => {
				return time.getTime() >= new Date("2999-12-30 23:59:59").getTime();
			}
		})
		return
	}

	this.pickerOptions = Object.assign({}, this.pickerOptions1,{
		disabledDate: time => {
			return (
				time.getTime() >
				new Date(this.endTime).getTime() - 24*3600*1000
			)
		}
	})
}