ng2_dnd_todolist.js

onDrop(src: Todo, trg: Todo) {
    this._moveRow(src.order, trg.order);
  }
  
  _moveRow(src, trg) {
    src = parseInt(src);
    trg = parseInt(trg);
    
    // If the element was moved down
    if (src > trg) {
      for (let i = trg; i < src; i++) {
        this.todos[i].order++;
      }
    } else {  // if the element was moved up
      for (let i = src + 1; i <= trg; i++) {
        this.todos[i].order--;
      }
    }
    this.todos[src].order = trg;
    this.todos.sort((a, b) => a.order - b.order);
  }