helloworld-samples/function-inline-nodejs/main.js

// ======================================================= //
//  IBM Cloud Code Engine - Functions-as-a-Service Sample  //
//                                                         //
//  main.js (NodeJS sample function)                       //
//                                                         //
//  Returns a simple HTML response, containing a message   //
//  that renders a greeting text. If the `name` parameter  //
//  was used to invoke the function, the given value       //
//  will be used in the greeting. If no `name` parameter   //
//  was used, a static text will be rendered instead.      //
//                                                         //
//  This sample shows how to access URL parameters in a    //
//  function.                                              //
//                                                         //
//  To pass a name to the function, which will be used     //
//  to render a personalized greeting, invoke the function //
//  with a parameter called 'name':                        //
//                                                         //
//  <function url>?name=<your name>                        //
//                                                         //
// ======================================================= //

/**
 * The `main` function is the entry-point into the function.
 * 
 * A function can define multiple functions, but it needs to
 * have one dedicated 'main' function, which will be called
 * by the runtime.
 * 
 * The 'main' function has one optional argument, which 
 * carries all the parameters the function was invoked with.
 * 
 * Those arguments are dynamic and can change between 
 * function invocations. 
 * 
 * Additionally, a function has access to some 
 * predefined and also user-defined environment variables.
 *  
 */ 
function main(params) {
  
  // the 'msg' variable carries our greeting text
  let msg;

  if (params.name) {
    // if an argument with name 'name' was given during 
    // function invocation, build a greeting for the given
    // name
    msg = `Hello, ${params.name}!`
  } else {
    // if no argument with name 'name' was found, use
    // a static greeting string instead
    msg = `Hello, Functions on CodeEngine!`
  }

  // finally, build an HTML response that can be rendered 
  // properly in a browser. To do so, we need to specify
  // the correct 'Content-Type' ('text/html' for HTML markup)
  // Alternatively, we could also use 'text/plain' or 
  // 'application/json', depending on the text we plan to 
  // return.
  return {
    // specify headers for the HTTP response
    // we only set the Content-Type in this case, to 
    // ensure the text is properly displayed in the browser
    headers: { 
      'Content-Type': 'text/html; charset=utf-8' 
    },
    // the body of the HTTP response carries the data, our
    // function wants to return
    // construct a very simple HTML page, which renders
    // the greeting string, we constructed earlier as a 
    // level 3 header
    body: `<html><body><h3>${msg}</h3></body></html>`
  }
}
  
// export the main function within this source file 
// as the 'main' symbol to make it known to the runtime
// This also works, if the function name is not 'main'.
// By exporting the function as 'main', it will be 
// found and invoked by the runtime.
//
// Example:
// function my_main_func_with_another_name(params) {
//    ...
// }
// ...
// // this also works!
// module.exports.main = my_main_func_with_another_name

module.exports.main = main;