如何去掉javascript中的重复项？

Question

注意:我知道我们使用Set来去掉数组中的重复项。

我有一个date dropdown.When我选择一个日期，它会在列表中正确地显示日期。

但问题是，如果我选择了一个已经选择的日期，它也会显示在列表中。我希望如果用户选择了一个已经选择的日期，它不应该添加到列表中，而是显示错误“你不能选择相同的日期”。

以下是代码-->

                 <Col md={12}>
                     <Datetime
                        timeFormat={false}
                        dateFormat={dateFormate}
                        // onChange={this.handleStartDate}
                        onBlur={this.handleStartDate}
                        onFocus={this.onFocus}
                      />
                   </Col>
                        {dateDay.map((dateday, dateDayindex) => (
                          <Col md={1} className="p-t-6">
                           {dateday.date}
                          </Col>
)}

//handleStartDate

handleStartDate = (date) => {
    const { dateDay } = this.state;
    const selectedDate = moment(date).format('DD/MM/YYYY');
    this.setState(
      {
        isSelectedDate: true,
      },
      () => {
        this.addDate(selectedDate);
      },
    );
  };
addDate = (selectedDate) => {
    const { dateDay } = this.state;
    const obj = { wday: '', interval: [], date: selectedDate, type: 'date' };

    const newInterval = { from: '9:00am', to: '10:00am', error: null };
    obj.interval.push(newInterval);
    arr.push(obj);
    if (arr.length > 1) {
      const isOverlaped = this.checkTimeOverlap(arr, arr.length - 1);
      if (isOverlaped) {
        newInterval.error = 'Time overlap with another set of times';
      }
      if (selectedDate === 'Invalid date') {
        newInterval.error = 'Please select a valid date';
      }
    }
    this.setState({ dateDay: arr });

Answer 1

在handleStartDate中进行验证，以检查所选日期是否已处于dateDay状态：

handleStartDate = (date) => {
    const { dateDay } = this.state;
    const selectedDate = moment(date).format('DD/MM/YYYY');

    // If selectedDate doesn't exist on the dateDay state, add it. Otherwise, show alert message
    if (!dateDay.find(obj => obj.date === selectedDate)) {
        this.setState(
            {
                isSelectedDate: true,
            },
            () => {
                this.addDate(selectedDate);
            },
        );
    } else {
        alert('You cannot choose the same date')
    }
};