Based on proposal by Dmitry Soshnikov on es-discuss mailing list

inline-doc-parse.js

(function( global ) {

  var rcomments = /\/\/.+?(?=\n|\r|$)|\/\*[\s\S]+?\*\//g;

  function getComments( fn ) {
    return ( fn.toString() || "" ).match( rcomments );
  };

  Object.defineProperty( Function.prototype, "__doc__", {
    get: function() {
      return getComments( this ).join("\n");
    },
    writeable: false,
    enumerable: true,
    configurable: false
  });

})( this );


// Example function with inline docs
function fnWithInlineDocs( obj /* an object */ ) {

  /*!
   * fnWithInlineDocs
   *
   * @param Object obj some kind of object
   *
   * @description returns the object param as an object
   *
   * @return the object
  */

  // This is a single line comment, that describes what happens next and why
  obj = Object(obj) || {};

  // Return the object
  return obj;
}


// Test
console.log(

  fnWithInlineDocs.__doc__

);

outcome.js

// without .join("\n"), as an array:
[
"/* an object */", 
"/*!
   * fnWithInlineDocs
   *
   * @param Object obj some kind of object
   *
   * @description returns the object param as an object
   *
   * @return the object
  */", 
"// This is a single line comment, that describes what happens next and why", 
"// Return the object"
]


// with .join("\n"), as a string:
/* an object */
/*!
   * fnWithInlineDocs
   *
   * @param Object obj some kind of object
   *
   * @description returns the object param as an object
   *
   * @return the object
  */
// This is a single line comment, that describes what happens next and why
// Return the object