Eliminate duplicate dropdown options in Angular 2 using a filter function

Question

Eliminate duplicate dropdown options in Angular 2 using a filter function

Is there a way to filter reporting results in an Angular 2 dropdown list? I am currently attempting to do so within the *ngFor template but haven't had any success. I will also try using a custom pipe. The data is coming from a JSON array. Specifically, in the example below, I am trying to display only one instance of "State Owned Entities".

This is my data object:

items[
      {  
       "currentBUName":"Financial Services"
      }
      {  
       "currentBUName":"State Owned Entities"
      }
      {  
       "currentBUName":"State Owned Entities"
      }
     ]

Here's an excerpt of my TypeScript code:

<ion-item>
     <ion-label>Please select current business unit</ion-label>
      <ion-select [(ngModel)]="selectedValue">
          <ion-option *ngFor="let indexx of this.items;"[value]="indexx">{{indexx.currentBUName}}</ion-option>
      </ion-select>
    </ion-item>

arrays angular typescript ionic2 angularjs-filter

Answer 1

Answer №1

To ensure that the values assigned to items are unique, you can utilize a filter function. Here's an example of how this can be achieved:

this.items = this.items.filter((value, index, array) => array.indexOf(value) === index);

Keep in mind: If the data is being retrieved from a server, it might be more efficient to perform this filtering on the server-side in order to minimize redundant information transmitted over the network.

Answer 2

To ensure that the values assigned to items are unique, you can utilize a filter function. Here's an example of how this can be achieved:

this.items = this.items.filter((value, index, array) => array.indexOf(value) === index);

Keep in mind: If the data is being retrieved from a server, it might be more efficient to perform this filtering on the server-side in order to minimize redundant information transmitted over the network.

Answer 3

Answer №2

Have you thought about utilizing the array filter method for this task?

items = [
  {  
   "currentBUName":"Financial Services"
  }
  {  
   "currentBUName":"State Owned Entities"
  }
  {  
   "currentBUName":"State Owned Entities"
  }
 ]
uniqueItems = items.filter(function(item, pos) {
    return items.indexOf(item) == pos;
})

You can then utilize the uniqueItems array instead.

Answer 4

Have you thought about utilizing the array filter method for this task?

items = [
  {  
   "currentBUName":"Financial Services"
  }
  {  
   "currentBUName":"State Owned Entities"
  }
  {  
   "currentBUName":"State Owned Entities"
  }
 ]
uniqueItems = items.filter(function(item, pos) {
    return items.indexOf(item) == pos;
})

You can then utilize the uniqueItems array instead.

Answer 5

Answer №3

While the previous solutions presented are effective, another approach is to create specific utility functions that can be applied more broadly.

function groupByUnique<T>(values: T[], keySelector: (value: T) => string): {[key: string]: T[]} {
  return values
      .map(value => ({ key: keySelector(value), value }))
      .reduce((groups, { key, value }) => ({
        ...groups,
        [key]: groups[key] && groups[key].concat(value) || [value]
      }), {});
}

function getDistinctValuesBy<T>(values: T[], keySelector: (value: T) => string): T[] {
  const groupedValues = groupByUnique(values, keySelector);
  return Object.values(groupedValues).map(([uniqueValue]) => uniqueValue);
}

Using these functions, you can then apply them like so:

this.filteredItems = getDistinctValuesBy(incomingData, data => data.propertyName);

Answer 6

While the previous solutions presented are effective, another approach is to create specific utility functions that can be applied more broadly.

function groupByUnique<T>(values: T[], keySelector: (value: T) => string): {[key: string]: T[]} {
  return values
      .map(value => ({ key: keySelector(value), value }))
      .reduce((groups, { key, value }) => ({
        ...groups,
        [key]: groups[key] && groups[key].concat(value) || [value]
      }), {});
}

function getDistinctValuesBy<T>(values: T[], keySelector: (value: T) => string): T[] {
  const groupedValues = groupByUnique(values, keySelector);
  return Object.values(groupedValues).map(([uniqueValue]) => uniqueValue);
}

Using these functions, you can then apply them like so:

this.filteredItems = getDistinctValuesBy(incomingData, data => data.propertyName);

Eliminate duplicate dropdown options in Angular 2 using a filter function

Answer №1

Answer №2

Answer №3

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