Simple Example to implement VS Code TreeDataProvider with JSON data

Here's a straightforward implementation:

import * as vscode from 'vscode';

export function activate(context: vscode.ExtensionContext) {
  vscode.window.registerTreeDataProvider('exampleView', new TreeDataProvider());
}

class TreeDataProvider implements vscode.TreeDataProvider<TreeItem> {
  onDidChangeTreeData?: vscode.Event<TreeItem|null|undefined>|undefined;

  data: TreeItem[];

  constructor() {
    this.data = [new TreeItem('cars', [
      new TreeItem(
          'Ford', [new TreeItem('Fiesta'), new TreeItem('Focus'), new TreeItem('Mustang')]),
      new TreeItem(
          'BMW', [new TreeItem('320'), new TreeItem('X3'), new TreeItem('X5')])
    ])];
  }

  getTreeItem(element: TreeItem): vscode.TreeItem|Thenable<vscode.TreeItem> {
    return element;
  }

  getChildren(element?: TreeItem|undefined): vscode.ProviderResult<TreeItem[]> {
    if (element === undefined) {
      return this.data;
    }
    return element.children;
  }
}

class TreeItem extends vscode.TreeItem {
  children: TreeItem[]|undefined;

  constructor(label: string, children?: TreeItem[]) {
    super(
        label,
        children === undefined ? vscode.TreeItemCollapsibleState.None :
                                 vscode.TreeItemCollapsibleState.Expanded);
    this.children = children;
  }
}

And in package.json:

{
    [...]
    "contributes": {
        "views": {
            "explorer": [
                {
                    "id": "exampleView",
                    "name": "exampleView"
                }
            ]
        }
    }
}

You might want to have a way of creating the data dynamically from your JSON data, but to keep the example as simple as possible I just create it statically in the constructor.