Demonstrates calling SharePoint search using SharePoint Framework HttpClient object with Promises (in TypeScript). See http://cob-sp.com/SPFX-Promises

SearchWithHttpClient_AndCaller.ts

// shows function first, then calling code below - note two functions are used here..

public GetResultsFromHttpClient (context: IWebPartContext, url: string): Promise<ISharePointSearchResults> {
  return context.httpClient.get(url, {
      // workaround for httpClient/search API issue..
      headers: {
        "odata-version": ""
      }}).then((response: Response) => {
      if (response.ok) {
          console.log("Returned OK from httpClient");
         return response.json();
      } else {
          console.log("WARNING - failed to hit URL " + url + ". Error = " + response.statusText);
      }
    });
}

public GetSearchResultsFromHttpClient (context: IWebPartContext, query: string, rowLimit: number): Promise<ISearchResult> {
	var self: Search = this;
  var url: string = self.getSearchUrl(query, rowLimit);

  return new Promise<ISearchResult>((resolve, reject) => {
    var results: SearchResult[] = new Array();
    self.GetResultsFromHttpClient(context, url).then((searchResults: ISharePointSearchResults) => {
      var relevantResults: ISharePointSearchResultsTable = (searchResults.PrimaryQueryResult !== null) ? searchResults.PrimaryQueryResult.RelevantResults.Table : null;
      if (relevantResults !== null) {
          console.log("Success executing search query. Fetched " + relevantResults.Rows.length + " results.");
          results = self.processSearchResults(relevantResults);
          resolve({Message: 'Success', Results: results});
      }
      else {
          var msg: string = "ERROR: No search results found!";
          console.log(msg);
          resolve({Message: msg, Results: results});
      }
    });
	});
}

// calling code:

Search.GetSearchResultsFromHttpClient(self.context, self.properties.searchQuery, self.properties.itemLimit).then((data) => {
  self.renderResults(data, self.domElement);
}).catch((response) => {
  console.log("Error getting results from httpClient - " + response);
});