Office OnReady in JSRuntime

onready.js

/**
 * Ensures the Office.js library is loaded.
 */
Office.onReady((info) => {
  /** 
   * Maps the event handler name specified in the manifest's LaunchEvent element to its JavaScript counterpart.
   * This ensures support in Outlook on Windows. 
   */
  if (Office.context.platform === Office.PlatformType.PC || Office.context.platform == null) {
    Office.actions.associate("onMessageSendHandler", onMessageSendHandler);
  }
});