Getting the Client Context for the file upload.

Step5-LargeFileUpload-GettingContext.js

function getWebRequestExecutorFactory(appWebUrl, hostWebUrl, spLanguage) {
  let context = new window.SP.ClientContext(appWebUrl);
  const factory = new window.SP.ProxyWebRequestExecutorFactory(appWebUrl);

  context.set_webRequestExecutorFactory(factory);

  return context;  
}

const jsomContext = (appWebUrl, hostWebUrl, spLanguage) => {
  return getWebRequestExecutorFactory(appWebUrl, hostWebUrl, spLanguage);
};

const jsomAppContext = (appWebUrl, hostWebUrl, spLanguage) => {
  let context = getWebRequestExecutorFactory(appWebUrl, hostWebUrl, spLanguage);
	
  // Use the host web URL to get a parent context - this allows us to get data from the parent
  let hostWebContext = new SP.AppContextSite(context, hostWebUrl);

  return hostWebContext;
};