Angular remove/filter 来自数组的重复国籍

Question

我有两个下拉选项，一个用于国家，一个用于国籍。两个下拉列表共享一个数组：countryAndNationalityList.

我试图只显示一次匹配的国籍，因为每个国家/地区都一样。

<select class="form-control" formControlName="residence_country">
    <option *ngFor="let item of removeNationalityDuplicates(countryAndNationalityList.sort(sortCountryAsc))" [ngValue]="item.country">{{item.country}}</option>
</select>

<select class="form-control" formControlName="nationality">
    <option value="" disabled>Your Nationality?</option>
    <option *ngFor="let item of countryAndNationalityList.sort(sortNationalityAsc)" [ngValue]="item.nationality">{{item.nationality}}</option>
</select>

我的 countryAndNationalityList 数组如下所示：

[{country: "United Arab Emirates Abu Dhabi", nationality: "Emirati"},
{country: "United Arab Emirates Ajman", nationality: "Emirati"},
{country: "United Arab Emirates Al-Quwain", nationality: "Emirati"},
{country: "United Arab Emirates Dubai", nationality: "Emirati"},
{country: "United Arab Emirates Fujairah", nationality: "Emirati"},
{country: "United Arab Emirates Ras Al Khaimah", nationality: "Emirati"},
{country: "United Arab Emirates Sharjah", nationality: "Emirati"}]

我正在尝试使用以下函数删除国籍下拉列表中重复的阿联酋：removeNationalityDuplicates 删除重复项，如下所示：

<select class="form-control" formControlName="nationality">
    <option value="" disabled>Your Nationality?</option>
    <option *ngFor="let item of removeNationalityDuplicates(countryAndNationalityList.sort(sortNationalityAsc))" [ngValue]="item.nationality">{{item.nationality}}</option>
</select>

removeNationalityDuplicates 在哪里

  removeNationalityDuplicates(array) {
    return [... new Set(array)];
  }

  sortNationalityAsc(previous, next) {
    return previous.nationality > next.nationality;
  }

我也试过使用：

removeNationalityDuplicates(array) {
  return array.reduce((uniqueArr, curVal)=> {
    if (!uniqueArr.includes(curVal.nationality)) {
      uniqueArr.push(curVal);
    }
    return uniqueArr;
  }, []);
}

如何去除重复的国籍？

Answer 1

removeNationalityDuplicates(array) {
  return Array.from(new Set(array.map(x => x.nationality)));
}

解释：

array.map(x => x.nationality) 创建一个只有 nationality 键的新数组
new Set(array.map(x => x.nationality)) 创建一组这个数组（像不同的一样工作）
Array.from(new Set(array.map(x => x.nationality))); 将集合转换为数组。

Answer 2

如果您正在寻找过滤原始数组但不更改其属性的可能性，请使用此解决方案：

const removeNationalityDuplicates = (arr) => [...new Map(arr.map(item => [item.nationality, item])).values()]


const list = [{
    country: "United Arab Emirates Abu Dhabi",
    nationality: "Emirati"
  },
  {
    country: "United Arab Emirates Ajman",
    nationality: "Emirati"
  },
  {
    country: "United Arab Emirates Al-Quwain",
    nationality: "Emirati"
  },
  {
    country: "United Arab Emirates Dubai",
    nationality: "Emirati"
  },
  {
    country: "United Arab Emirates Fujairah",
    nationality: "Emirati"
  },
  {
    country: "United Arab Emirates Ras Al Khaimah",
    nationality: "Emirati"
  },
  {
    country: "United Arab Emirates Sharjah",
    nationality: "Emirati"
  }
]

console.log(removeNationalityDuplicates(list))

如果您只想获得国籍列表，请查看。

Angular remove/filter 来自数组的重复国籍

Angular remove/filter duplicate nationality from array

javascript

arrays

angular

duplicates

ngfor