refactor histogram calc - use variable

Author: archmoj

src/traces/histogram/calc.js

@@ -15,8 +15,9 @@ var getBinSpanLabelRound = require('./bin_label_vals');
 function calc(gd, trace) {
     var pos = [];
     var size = [];
-    var pa = Axes.getFromId(gd, trace.orientation === 'h' ? trace.yaxis : trace.xaxis);
-    var mainData = trace.orientation === 'h' ? 'y' : 'x';
+    var isHorizontal = trace.orientation === 'h';
+    var pa = Axes.getFromId(gd, isHorizontal ? trace.yaxis : trace.xaxis);
+    var mainData = isHorizontal ? 'y' : 'x';
     var counterData = {x: 'y', y: 'x'}[mainData];
     var calendar = trace[mainData + 'calendar'];
     var cumulativeSpec = trace.cumulative;