vue+elementui 只能选7天内的日期

html: 

   <el-col :span="2">查询时间</el-col>
      <el-col :span="6">
        <el-date-picker
          v-model="checkParams.startDate"
          type="date"
          placeholder="开始时间"
          format="yyyy-MM-dd"
          value-format="yyyy-MM-dd"
          style="width:45%"
          :picker-options="pickerStart"
        />
        <span style="padding: 0 1%;">至</span>
        <el-date-picker
          v-model="checkParams.endDate"
          format="yyyy-MM-dd"
          value-format="yyyy-MM-dd"
          type="date"
          placeholder="结束时间"
          style="width:45%"
          :picker-options="pickerEnd"
        />
      </el-col>

js:

 data() {
    const _this = this;
    const dateScope = 7 * 24 * 3600 * 1000;
    return {
      pickerStart: {
        disabledDate(time) {
          if (_this.checkParams.endDate != "") {
            /**
             * 如果另一个框有值,就只能选7天内的日期
             *
             */
            let date = new Date(_this.checkParams.endDate).getTime();
            return (
              time.getTime() < date - dateScope ||
              time.getTime() > dateScope + date
            );
          }
          return time.getTime() > Date.now();
        }
      },
      pickerEnd: {
        disabledDate(time) {
          if (_this.checkParams.startDate != "") {
            let date = new Date(_this.checkParams.startDate).getTime();
            return (
              time.getTime() < date - dateScope ||
              time.getTime() > dateScope + date
            );
            return;
          }
          return time.getTime() > Date.now();
        }
      },}