Illustration of provider idiom in Javascript for sharing with fellow Code PaLOUsa 2011 conference attendee from this morning #CPL11

provider_example.js

/*
 * Javascript provider idiom illustrated
 * @author Susan Potter
 * @date   2011-01-28
 */

// FinEnv "interface"
var FinEnv = function () {
  return {
    println: function (output) {
               // TODO: impelment for each env provider
             },
    print: function (output) {
             // TODO: implement for each env provider
           },
    require: function (include) {
               // TODO: implement for each env provider
             }
  }
}();

// included for browser environment
(function (envBase) {
  envBase.println = function (output) {
    document.write('<p>' + output + '</p>');
  };
  envBase.print = function (output) {
    document.write('<br>' + output);
  };
  envBase.require = function (include) {
    document.write('<script src="' + include + '"></script');
  };
  return envBase;
}) (FinEnv);

// included for Rhino environment
(function (envBase) {
  envBase.println = function (output) {
    print(output + '\n');
  };
  envBase.print = function (output) {
    print(output);
  };
  envBase.require = function (include) {
    require(include);
  };
  return envBase;
}) (FinEnv);

// included for NodeJS environment
(function (envBase) {
  envBase.println = function (output) {
    console.log(output + '\n');
  };
  envBase.print = function (output) {
    require('util').print(output);
  };
  envBase.require = function (include) {
    require(include);
  };
  return envBase;
}) (FinEnv);

// included for FreeSWITCH environment
(function (envBase) {
  envBase.println = function (output) {
    console_log(output + '\n');
  };
  envBase.print = functiion (output) {
    console_log(output);
  };
  envBase.require = function (include) {
    use(include);
  };
}) (FinEnv);

// in application code can run in browser, Rhino or NodeJS now!
FinEnv.println("This blows my mind.");