code: function(str, value, start, end) {
  			if (typeof start === 'object' && 'end' in start) {
  				end = start.end;
  				start = start.start;
  			}
  			
  			if (typeof end === 'string') {
  				end = start + end.length;
  			}
  			
  			if (typeof end === 'undefined') {
  				end = start;
  			}
  			
  			if (start < 0 || start > str.length)
  				return str;
  			
  			return str.substring(0, start) + value + str.substring(end);
  		}
docs: Replace substring of <code>str</code> with <code>value</code>
  @param {String} str String where to replace substring
  @param {String} value New substring value
  @param {Number} start Start index of substring to replace. May also
  be a <code>Range</code> object: in this case, the <code>end</code>
  argument is not required
  @param {Number} end End index of substring to replace. If ommited,
  <code>start</code> argument is used