Using lambda expressions in Angular to streamline complex iteration processes

Is there an easy way to shorten this code block:

  this.markersDisplay = this.markersSource;

    // Filter Marker Type
    if (this.isValid(this.selectedMarkersType)) {
      let markers: Array<Marker> = new Array<Marker>();
      for (let marker of this.markersDisplay) {
        for (let markerType of this.selectedMarkersType) {
          if (marker.MarkerType == markerType) {
            markers.push(marker);
            break;
          }
        }
      }
      this.markersDisplay = markers;
    }

I want to find a more concise way to replace the double for loop with a lambda expression

angulartypescript

Answer №1

If the break statement is not necessary, you can utilize this method:

markers = this.markersDisplay
    .filter((marker: Marker) => (this.selectedMarkersType
            .find((markerType: MarkerType) => markerType === marker.MarkerType)));

If working without types:

markers = this.markersDisplay
    .filter(marker => (this.selectedMarkersType
            .find(markerType => markerType === marker.MarkerType)));

If you require the break statement for performance reasons and cannot use arrow functions, consider using some() or every() functions:

markers = this.markersDisplay
    .filter(marker => (this.selectedMarkersType
            .some(markerType => markerType === marker.MarkerType)));

This functionality is demonstrated in this stackblitz example

Answer №2

Give this a shot:

markers = markersDisplay.filter(y=>{
    return selectedMarkersType.find((value,idx)=>{
        return y.MarkerType==value;
    })
});

Answer №3

After analyzing your data structure, I have made some assumptions in order to provide you with the following code solution.

this.markersDisplay.forEach((point) => {
        point.MarkerType.filter(item => item.MarkerType === this.selectedMarkersType).map(item => markers.push(marker));
      });

Answer №4

It is recommended to utilize the Array.forEach method for this task.

this.displayedMarkers = this.sourceMarkers;

// Filtering Marker Type
if (this.isAppropriate(this.selectedMarkerTypes)) {
  let filteredMarkers: Array<Marker> = new Array<Marker>();
  this.displayedMarkers.forEach(dm => {
    this.selectedMarkerTypes.forEach(mt => {
      if (dm.type === mt) {
        filteredMarkers.push(dm);
      }
    });
  });
  this.displayedMarkers = filteredMarkers;
}

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