old_contents: /**
   * source.js
   * Andrea Tino - 2015
   */
  
  /**
   * Extracts parts from the source code basing on line number and column number.
   * _src: Source code to provide
   */
  module.exports = function(_src) {
    var validateSrc = function(src) {
      if (!src) {
        throw 'Error: src cannot be null or undefined!';
      }
      return src;
    };
    
    var src = validateSrc(_src);
  
    return {
      /**
       * Extracts source code at provided line number and col number.
       * rs: Row start.
       * re: Row end.
       * cs: Col start.
       * ce: Col end.
       */
      at: function(rs, re, cs, ce) {
        
      }
    };
  };
  
new_contents: /**
   * source.js
   * Andrea Tino - 2015
   */
  
  /**
   * Extracts parts from the source code basing on line number and column number.
   * _src: Source code to provide
   */
  module.exports = function(_src) {
    var validateSrc = function(src) {
      if (!src || src.lenght <= 0) {
        throw 'Error: src cannot be null, undefined or an empty string!';
      }
      return src;
    };
    
    var src = validateSrc(_src);
  
    return {
      /**
       * Extracts source code at provided line number and col number.
       * rs: Row start.
       * re: Row end.
       * cs: Col start.
       * ce: Col end.
       */
      at: function(rs, re, cs, ce) {
        if (!rs || typeof rs !== 'number') {
          throw 'Error: Row start must be a number!';
        }
        if (!re || typeof re !== 'number') {
          throw 'Error: Row end must be a number!';
        }
        if (!cs || typeof cs !== 'number') {
          throw 'Error: Col start must be a number!';
        }
        if (!ce || typeof ce !== 'number') {
          throw 'Error: Col end must be a number!';
        }
        if (re < rs) {
          throw 'Error: Row end must be greater or equal than row start!';
        }
        if (ce < cs) {
          throw 'Error: Col end must be greater or equal than col start!';
        }
      }
    };
  };
  
subject: Update source.js