replace unnecessary === undefined check in Plots

  by simple `!` checks

Author: etpinard

src/plots/plots.js

@@ -63,7 +63,7 @@ plots.hasSimpleAPICommandBindings = commandModule.hasSimpleAPICommandBindings;
 plots.findSubplotIds = function findSubplotIds(data, type) {
     var subplotIds = [];
 
-    if(plots.subplotsRegistry[type] === undefined) return subplotIds;
+    if(!plots.subplotsRegistry[type]) return subplotIds;
 
     var attr = plots.subplotsRegistry[type].attr;
 
@@ -90,7 +90,7 @@ plots.findSubplotIds = function findSubplotIds(data, type) {
 plots.getSubplotIds = function getSubplotIds(layout, type) {
     var _module = plots.subplotsRegistry[type];
 
-    if(_module === undefined) return [];
+    if(!_module) return [];
 
     // layout must be 'fullLayout' here
     if(type === 'cartesian' && (!layout._has || !layout._has('cartesian'))) return [];
@@ -131,7 +131,7 @@ plots.getSubplotIds = function getSubplotIds(layout, type) {
  *
  */
 plots.getSubplotData = function getSubplotData(data, type, subplotId) {
-    if(plots.subplotsRegistry[type] === undefined) return [];
+    if(!plots.subplotsRegistry[type]) return [];
 
     var attr = plots.subplotsRegistry[type].attr,
         subplotData = [],
@@ -167,7 +167,7 @@ plots.getSubplotData = function getSubplotData(data, type, subplotId) {
  * @return {array} array of calcdata traces
  */
 plots.getSubplotCalcData = function(calcData, type, subplotId) {
-    if(plots.subplotsRegistry[type] === undefined) return [];
+    if(!plots.subplotsRegistry[type]) return [];
 
     var attr = plots.subplotsRegistry[type].attr;
     var subplotCalcData = [];