improve code readability

Author: antoinerg

Diff for: src/components/colorscale/calc.js

@@ -15,6 +15,7 @@ var flipScale = require('./flip_scale');
 
 
 module.exports = function calc(gd, trace, opts) {
+    var fullLayout = gd._fullLayout;
     var vals = opts.vals;
     var containerStr = opts.containerStr;
     var cLetter = opts.cLetter;
@@ -86,8 +87,8 @@ module.exports = function calc(gd, trace, opts) {
     doUpdate(autoAttr, (auto !== false || (min === undefined && max === undefined)));
 
     if(container.autocolorscale) {
-        if(min * max < 0) scl = gd._fullLayout.colorscale.diverging;
-        else if(min >= 0) scl = gd._fullLayout.colorscale.sequential;
+        if(min * max < 0) scl = fullLayout.colorscale.diverging;
+        else if(min >= 0) scl = fullLayout.colorscale.sequential;
         else scl = gd._fullLayout.colorscale.sequentialminus;
 
         // reversescale is handled at the containerOut level