splice is creating NULL entry while removing the entry from an array

Question

In my Angular5 application when I tried to remove the entries from the peoples array which is contained in selectedPersonArray using splice keyword is occasionally creating null entry in the peoples array. The code I have done looks like this:

import { Component } from '@angular/core';
import { DragulaService } from 'ng2-dragula/ng2-dragula';
 @Component({
 selector: 'app-root',
 templateUrl: './app.component.html',
 styleUrls: ['./app.component.css']
 })
 export class AppComponent {


    selectedPersonArray = [];
    peoples = [
    {
      id: 7,
      firstName: 'Sobin 7',
      lastName: 'Thomas 7'
   }
  ];
 people = [
  {
  id: 1,
  firstName: 'First Name 1',
  lastName: 'Last Name 1'
},
{
  id: 2,
  firstName: 'First Name 2',
  lastName: 'Last Name 2'
},
{
  id: 3,
  firstName: 'First Name 3',
  lastName: 'Last Name 3'
},
{
  id: 4,
  firstName: 'First Name 4',
  lastName: 'Last Name 4'    
 }
];

  toggleItemInArr(arr, item) {
   const index = arr.indexOf(item);
   index === - 1 ? arr.push(item) : arr.splice(index, 1);
  }

 addThisPersonToArray(person: any, event) {
  if (!event.ctrlKey) {
    this.selectedPersonArray = [];
  }

  this.toggleItemInArr(this.selectedPersonArray, person);
 }

 isPersonSelected(person: any) {
   return (this.selectedPersonArray.indexOf(person) !== -1);
 }

constructor(private dragula: DragulaService) { 
  dragula.setOptions('second-bag', {
   copy: function (el, source) {
   return source.id === 'source';
  },

removeOnSpill: true,

copySortSource: false,
accepts: function(el, target, source, sibling) {
return target.id !== 'source';
}
});


}
ngOnInit() {
 this.dragula
  .out
  .subscribe(value => {

  for(let select of  this.selectedPersonArray){
    let i= 0;         
     for (let entry of this.peoples) {
         if(entry.id == select.id){               
           let index = this.people.indexOf(select.id);            
           if (this.peoples.length >0){
             this.peoples.splice(i, 1);
           }               
          }             
     i++;
    }         
  }
  console.log("on after loop   "+JSON.stringify( this.peoples));
  this.selectedPersonArray.length = 0; 

 });    
 } 
}

app.component.html

<table border=1 bgcolor="yellow">
  <tbody id ='source' [dragula]='"second-bag"' [dragulaModel]="people">
    <tr *ngFor="let person of people" >
      <td>{{person.id}}</td>
      <td>{{person.firstName}}</td>
      <td>{{person.lastName}}</td>
    </tr>
  </tbody>
</table>




 <table border=2>
  <tbody id ='dest' [dragula]='"second-bag"' [dragulaModel]="peoples">
    <tr *ngFor="let person of peoples" (click)="addThisPersonToArray(person, $event)" [class.active]="isPersonSelected(person)">
      <td>{{person.id}}</td>
      <td>{{person.firstName}}</td>
      <td>{{person.lastName}}</td>
    </tr>
  </tbody>
</table>

Actually what I want was is to delete multiple items selected using control key from 'dest' container of ng2-dragular second-bag.And it is working but it is creating null entries also

Answer 1

I like the answer using filter and find. Here's another alternative using a loop.

I worked on a jsfiddle with what I suspect you were trying to do. Is this this is similar to what you intended?

I updated the search to work backwards so that the splice wouldn't alter the parts of the array that had not been searched through yet.

The jsfiddle can be found here: https://jsfiddle.net/vboughner/wfeunv2j/

this.selectedPersonArray = [
  {
    "id": "hello1",
    "name": "something1"
  },
];

this.peoples = [
  {
    "id": "hello1",
    "name": "something1"
  },
  {
    "id": "hello2",
    "name": "something2"
  },
  {
    "id": "hello3",
    "name": "something3"
  },
];
console.log(this.selectedPersonArray);
console.log(this.peoples);

for (let select of this.selectedPersonArray) {
  for (let i = this.peoples.length - 1; i >= 0; i--) {
    if (select.id == this.peoples[i].id) {
      this.peoples.splice(i, 1);
    }
  }
}

console.log("on after loop   " + JSON.stringify( this.peoples));
this.selectedPersonArray.length = 0; 

The output looks like this:

on after loop   [{"id":"hello2","name":"something2"},{"id":"hello3","name":"something3"}]

Answer 2

Can you try this?

this.peoples
    .filter(people => !this.selectedPersonArray
        .find(selectdPeople => people.id === selectdPeople.id)
    );