ng-sortablejs/src/lib/sortablejs-binding.ts

import {SortableData} from './sortablejs.directive';

export class SortablejsBinding {

  constructor(private target: SortableData) {
  }

  insert(index: number, item: any) {
    if (this.isFormArray) {
      this.target.insert(index, item);
    } else {
      this.target.splice(index, 0, item);
    }
  }

  get(index: number) {
    return this.isFormArray ? this.target.at(index) : this.target[index];
  }

  remove(index: number) {
    let item;

    if (this.isFormArray) {
      item = this.target.at(index);
      this.target.removeAt(index);
    } else {
      item = this.target.splice(index, 1)[0];
    }

    return item;
  }

  // we need this to identify that the target is a FormArray
  // we don't want to have a dependency on @angular/forms just for that
  private get isFormArray() {
    // just checking for random FormArray methods not available on a standard array
    return !!this.target.at && !!this.target.insert && !!this.target.reset;
  }

}