refactored out manual flattening to .flat(..)

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>

ui (gen4)/features/collections.js

@@ -847,7 +847,7 @@ var CollectionActions = actions.Actions({
 						: [ that.data.getImage(gid) 
 							// check base data for image gid...
 							|| that.collections[MAIN_COLLECTION_TITLE].data.getImage(gid) ] })
-				.reduce(function(a, b){ return a.concat(b) }, [])
+				.flat()
 
 			this.ensureCollection(collection)
 				.then((function(c){
@@ -1040,7 +1040,7 @@ var CollectionActions = actions.Actions({
 						// when adding a ribbon gid expand to images...
 						that.data.ribbons[gid].compact()
 						: [that.data.getImage(gid)] })
-				.reduce(function(a, b){ return a.concat(b) }, [])
+				.flat()
 
 			// remove from the loaded state...
 			this.collection == collection

ui (gen4)/features/sort.js

@@ -136,8 +136,7 @@ module.SortActions = actions.Actions({
 								.filter(function(e){ 
 									return e && e.trim() != '' && !/['"]/.test(e) }) 
 						: [])
-					.reduce(function(r, e){
-						return r.concat(e instanceof Array ? e : [e]) }, []) }
+					.flat() }
 			var get = function(name){
 				// normalize name...
 				name = name
@@ -196,9 +195,7 @@ module.SortActions = actions.Actions({
 						: a instanceof Array ?
 							a
 						: method })
-				// merge...
-				.reduce(function(r, e){
-					return r.concat(e instanceof Array ? e : [e]) }, []) }],
+				.flat() }],
 
 	// Custom sort methods...
 	//
@@ -783,8 +780,7 @@ var SortUIActions = actions.Actions({
 									function(e){ 
 										return expandMethods(e)[0] || [] } 
 									: expandMethods)
-								.reduce(function(r, e){
-									return r.concat(e instanceof Array ? e : [e]) }, [])
+								.flat()
 								.map(function(e){ 
 									return indent + e })
 						: typeof(methods) == typeof('str') ?

ui (gen4)/features/tags.js

@@ -223,8 +223,7 @@ var TagUIActions = actions.Actions({
 			gids = gids
 				.map(function(gid){
 					return gid == 'marked' ? that.marked : gid })
-				.reduce(function(res, cur){
-					return res.concat(cur instanceof Array ? cur : [cur]) }, [])
+				.flat()
 				.unique()
 
 			// XXX

ui (gen4)/features/ui-widgets.js

@@ -1144,7 +1144,7 @@ var UIIntrospectionActions = actions.Actions({
 						.html('Handlers: '
 							+ (feature.handlers || [['-']])
 								.map(function(h){ return h[0] instanceof Array ? h[0] : [h[0]] })
-								.reduce(function(a, b){ return a.concat(b) }, [])
+								.flat()
 								.unique()
 								.map(function(n){
 									return n == '-' ? n : action2lnk(n) })