Move plus/minus key list to utilKeybinding property

modules/ui/zoom.js

@@ -7,6 +7,7 @@ import { t, localizer } from '../core/localizer';
 import { svgIcon } from '../svg/icon';
 import { uiCmd } from './cmd';
 import { uiTooltip } from './tooltip';
+import { utilKeybinding } from '../util/keybinding';
 
 
 export function uiZoom(context) {
@@ -95,12 +96,12 @@ export function uiZoom(context) {
                 .call(svgIcon('#' + d.icon, 'light'));
         });
 
-        ['plus', 'ffplus', '=', 'ffequals'].forEach(function(key) {
+        utilKeybinding.plusKeys.forEach(function(key) {
             context.keybinding().on([key], zoomIn);
             context.keybinding().on([uiCmd('⌥' + key)], zoomInFurther);
         });
 
-        ['_', '-', 'ffminus', 'dash'].forEach(function(key) {
+        utilKeybinding.minusKeys.forEach(function(key) {
             context.keybinding().on([key], zoomOut);
             context.keybinding().on([uiCmd('⌥' + key)], zoomOutFurther);
         });

modules/util/keybinding.js

@@ -214,6 +214,9 @@ utilKeybinding.modifierProperties = {
     91: 'metaKey'
 };
 
+utilKeybinding.plusKeys = ['plus', 'ffplus', '=', 'ffequals'];
+utilKeybinding.minusKeys = ['_', '-', 'ffminus', 'dash'];
+
 utilKeybinding.keys = {
     // Backspace key, on Mac: ⌫ (Backspace)
     '⌫': 'Backspace', backspace: 'Backspace',