fix examples under old node versions
fix examples under old node versions
jupyter/jupyter-js-notebook,blink1073/jupyter-js-notebook,blink1073/jupyter-js-notebook,jupyter/jupyter-js-notebook,blink1073/jupyter-js-notebook,blink1073/jupyter-js-notebook,jupyter/jupyter-js-notebook,jupyter/jupyter-js-notebook,blink1073/jupyter-js-notebook,jupyter/jupyter-js-notebook