disable checkbox in angular tree component

Disabling the node can be done by actionMapping inside options attribute https://angular2-tree.readme.io/v1.2.0/docs/options. Here click event of mouse can be overwritten.

<Tree  [nodes]="nodes"  [options]="treeOptions"></Tree>

In my tree data I kept an attribute isSelectable on each node, which is true|false. In case of true i proceed selecting the node otherwise it does not do anything. Here are full options that I am passing to the tree component.

public options: ITreeOptions = {
    isExpandedField: 'expanded',
    idField: 'uuid',
    getChildren: this.getChildren.bind(this),
    actionMapping: {
      mouse: {
        click: (tree, node, $event) => {
          if ( node.data.isSelectable ) {
            this.isNodeSelected.emit(node.data);
            this.alreadySelected = true;
            this.preSelected.tree = tree;
            this.preSelected.node = node;
            this.preSelected.event = $event;
            TREE_ACTIONS.ACTIVATE(this.preSelected.tree, this.preSelected.node, this.preSelected.event);
          }
        }
      }
    },
    nodeHeight: 23,
    allowDrag: (node) => {
      return false;
    },
    allowDrop: (node) => {
      return false;
    }
};