fix syntax

color.cm

@@ -181,24 +181,30 @@ ColorMap.Viridis = ColorMap.makemap({
 
 Color.normalize(ColorMap);
 
-ColorMap.sample = function(t, map = this) {
-  if (t < 0) return map[0]
-  if (t > 1) return map[1]
+ColorMap.sample = function(t, map) {
+  var local_map = map || this
+  if (t < 0) return local_map[0]
+  if (t > 1) return local_map[1]
 
-  var keys = sorted(array(map))
+  var keys = sorted(array(local_map))
   var lastkey = 0
+  var i = 0
+  var key = null
+  var b = null
+  var a = null
+  var tt = 0
 
-  for (var i = 0; i < length(keys); i++) {
-    var key = keys[i]
+  for (i = 0; i < length(keys); i++) {
+    key = keys[i]
     if (t < key) {
-      var b = map[key]
-      var a = map[lastkey]
-      var tt = (t - lastkey) / (key - lastkey)
+      b = local_map[key]
+      a = local_map[lastkey]
+      tt = (t - lastkey) / (key - lastkey)
       return a.lerp(b, tt)
     }
     lastkey = key
   }
-  return map[1]
+  return local_map[1]
 }
 
 ColorMap.doc = {