el-date-picker设置日期默认值两种方法(当月月初至月末)

        <el-date-picker
          v-model="queryParams.signDate"
          type="daterange"
          align="right"
          unlink-panels
          size="small"
          value-format="yyyy-MM-dd"
          format="yyyy-MM-dd"
          range-separator="至"
          start-placeholder="开始日期"
          end-placeholder="结束日期"
          :picker-options="pickerOptions">
        </el-date-picker>

<script>
export default {
  data() {
    return {
      queryParams: {  
        signDate: ''
      },
      pickerOptions: {
        shortcuts: [{
          text: '最近一周',
          onClick(picker) {
            const end = new Date()
            const start = new Date()
            start.setTime(start.getTime() - 3600 * 1000 * 24 * 7)
            picker.$emit('pick', [start, end])
          }
        }, {
          text: '最近一个月',
          onClick(picker) {
            const end = new Date()
            const start = new Date()
            start.setTime(start.getTime() - 3600 * 1000 * 24 * 30)
            picker.$emit('pick', [start, end])
          }
        }, {
          text: '最近三个月',
          onClick(picker) {
            const end = new Date()
            const start = new Date()
            start.setTime(start.getTime() - 3600 * 1000 * 24 * 90)
            picker.$emit('pick', [start, end])
          }
        }]
      }
    }
  },
  created() {
    // 初始化默认时间
    this.defaultDate()
  },
  methods: {
    // 初始化默认时间
    defaultDate() {
      var date = new Date()
      var year = date.getFullYear().toString()
      var month = date.getMonth() + 1 < 10 ? '0' + (date.getMonth() + 1).toString() : (date.getMonth() + 1).toString()
      // var da = date.getDate() < 10 ? '0' + date.getDate().toString() : date.getDate().toString()
      var da = new Date(date.getFullYear(), month, 0).getDate()
      da < 10 ? '0' + da.toString() : da.toString()
      var beg = year + '-' + month + '-01'
      var end = year + '-' + month + '-' + da
      this.queryParams.signDate = [beg, end] //将值设置给插件绑定的数据
    }
  },
  watch: {
    // 监听日期清理后数据为null进行处理否则会报错
    'queryParams.signDate'(newVal) {
      if (newVal == null) {
        this.queryParams.signDate = ''
        this.queryParams.startTime = ''
        this.queryParams.endTime = ''
      }
    }
  }
}
</script>

<el-form-item  prop="startTime" style="margin-left: 20px">
        <el-date-picker
          v-model="queryParams.startTime"
          type="date"
          size="small"
          placeholder="开始日期"
          value-format="yyyy-MM-dd"
          format="yyyy-MM-dd"
          style="width: 130px"
          :picker-options="pickerOptionsStart"
        >
        </el-date-picker>
      </el-form-item>
      <el-form-item label="至" prop="endTime">
        <el-date-picker
          v-model="queryParams.endTime"
          type="date"
          size="small"
          placeholder="结束日期"
          value-format="yyyy-MM-dd"
          format="yyyy-MM-dd"
          style="width: 130px"
          :picker-options="pickerOptionsEnd"
        >
        </el-date-picker>
      </el-form-item>

<script>
export default {
  data() {
    return {
      queryParams: {
        startTime: '',
        endTime: '',
      },
      // 开始时间不能大于结束时间
      pickerOptionsStart: {
        disabledDate: (time) => {
          if (this.queryParams.endTime) {
            return (
              time.getTime() >= new Date(this.queryParams.endTime).getTime()
            )
          }
        }
      },
      // 结束时间不能小于开始时间
      pickerOptionsEnd: {
        disabledDate: (time) => {
          if (this.queryParams.startTime) {
            return (
              time.getTime() <= new Date(this.queryParams.startTime).getTime()
            )
          }
        }
      }
    }
  },
  created() {
    /** 重置按钮操作 */
    resetForm() {
      this.$refs['formName'].resetFields()
      this.queryParams.startTime = ''
      this.queryParams.endTime = ''
    },
    // 初始化默认时间
    defaultDate() {
      var date = new Date()
      var year = date.getFullYear().toString()
      var month = date.getMonth() + 1 < 10 ? '0' + (date.getMonth() + 1).toString() : (date.getMonth() + 1).toString()
      // var da = date.getDate() < 10 ? '0' + date.getDate().toString() : date.getDate().toString()
      var da = new Date(date.getFullYear(), month, 0).getDate()
      da < 10 ? '0' + da.toString() : da.toString()
      var beg = year + '-' + month + '-01'
      var end = year + '-' + month + '-' + da
      this.queryParams.startTime = beg //将值设置给插件绑定的数据
      this.queryParams.endTime = end
    }
  },
  watch: {
    // 监听日期清理后数据为null进行处理否则会报错
    'queryParams.startTime'(newVal) {
      if (newVal == null) {
        this.queryParams.startTime = ''
      }
    },
    'queryParams.endTime'(newVal) {
      if (newVal == null) {
        this.queryParams.endTime = ''
      }
    }
  }
}
</script>