add your own tokens to the patternLayout

lib/layouts.js

@@ -10,8 +10,9 @@ var dateFormat = require('./date_format')
     , "coloured": function() { return colouredLayout; }
     , "pattern": function (config) {
 	  var pattern = config.pattern || undefined;
-	  return patternLayout(pattern);
-      }
+	  var tokens = config.tokens || undefined;
+	  return patternLayout(pattern, tokens);
+	}
   }
   , colours = {
       ALL: "grey"
@@ -143,9 +144,9 @@ function messagePassThroughLayout (loggingEvent) {
  * Takes a pattern string and returns a layout function.
  * @author Stephan Strittmatter
  */
-function patternLayout (pattern) {
+function patternLayout (pattern, tokens) {
     var TTCC_CONVERSION_PATTERN  = "%r %p %c - %m%n";
-    var regex = /%(-?[0-9]+)?(\.?[0-9]+)?([\[\]cdmnpr%])(\{([^\}]+)\})?|([^%]+)/;
+    var regex = /%(-?[0-9]+)?(\.?[0-9]+)?([\[\]cdmnprx%])(\{([^\}]+)\})?|([^%]+)/;
 
     pattern = pattern || TTCC_CONVERSION_PATTERN;
 
@@ -221,6 +222,17 @@ function patternLayout (pattern) {
 		case "%":
 		    replacement = "%";
 		    break;
+		case "x":
+			if(tokens[specifier]) {
+				if(typeof(tokens[specifier]) === 'function') {
+					replacement = tokens[specifier]();
+				} else {
+					replacement = tokens[specifier];
+				}
+			} else {
+				replacement = matchedString;
+			}
+			break;
 		default:
 		    replacement = matchedString;
 		    break;