Google Apps Script template functions for external host communication with UrlFetchApp. See https://mogsdad.wordpress.com.

httpGetTemplate.gs

/** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * httpGetTemplate.gs
 *
 * A pair of template functions for external host communication with
 * UrlFetchApp, including parameter encoding and error handling.
 *
 * From: gist.github.com/mogsdad/a76c32231a2b91ff8b59
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
   
 /**
 * Template function for performing HTTP GET, with error handling.
 * 
 * From: gist.github.com/mogsdad/a76c32231a2b91ff8b59
 */
function httpGetTemplate() {
  // URL for target web API
  var url = 'https://example.com/apis/--apiId--';

  // For GET method, API parameters will be sent in the URL. 
  // Start with an object containing name / value tuples.
  var apiParams = {
    // Relevant parameters would go here
    'param1' : 'value1',
    'param2' : 'value2'   // etc.
  };

  // For GET, Encode params object as a URI escaped query string
  var encParams = toHtmlQuery_(apiParams);
  
  // Construct `fetch` params object
  var params = {
    'method': 'GET',              // This is redundant; GET is default
    'muteHttpExceptions' : true
  };
  
  var response = UrlFetchApp.fetch(url+encParams, params)

  // Check return code embedded in response.
  var rc = response.getResponseCode();
  var responseText = response.getContentText();
  if (rc !== 200) {
    // Log HTTP Error
    Logger.log("Response (%s) %s",
               rc,
               responseText );
    // Could throw an exception yourself, if appropriate
  }
  else {
    // Successful POST, handle response normally
    Logger.log( responseText );
  }
}

 /**
 * Template function for performing HTTP POST, with error handling.
 * 
 * From: gist.github.com/mogsdad/a76c32231a2b91ff8b59
 */
function httpPostTemplate() {
  // URL for target web API
  var url = 'https://example.com/apis/--apiId--';

  // For POST method, API parameters will be sent in the
  // HTTP message payload.
  // Start with an object containing name / value tuples.
  var apiParams = {
    // Relevant parameters would go here
    'param1' : 'value1',
    'param2' : 'value2'   // etc.
  };

  // All 'application/json' content goes as a JSON string.
  var payload = JSON.stringify(apiParams);

  // Construct `fetch` params object
  var params = {
    'method': 'POST',
    'contentType': 'application/json',
    'payload': payload,
    'muteHttpExceptions' : true
  };
  
  var response = UrlFetchApp.fetch(url, params)

  // Check return code embedded in response.
  var rc = response.getResponseCode();
  var responseText = response.getContentText();
  if (rc !== 200) {
    // Log HTTP Error
    Logger.log("Response (%s) %s",
               rc,
               responseText );
    // Could throw an exception yourself, if appropriate
  }
  else {
    // Successful POST, handle response normally
    Logger.log( responseText );
  }
}

/**
 * Generate HTML query string from given object
 * Adapted from http://stackoverflow.com/a/18116302/1677912
 */
function toHtmlQuery_(obj) {return "?"+Object.keys(obj).reduce(function(a,k){a.push(k+'='+encodeURIComponent(obj[k]));return a},[]).join('&')};