declare and reuse stamen attribution string

Author: archmoj

src/plots/mapbox/constants.js

@@ -3,6 +3,7 @@
 var requiredVersion = '1.10.1';
 
 var OSM = '<a href="https://www.openstreetmap.org/copyright" target="_blank">© OpenStreetMap</a> contributors';
+var stamen = 'Map tiles by <a href="https://stamen.com">Stamen Design</a>, under <a href="https://creativecommons.org/licenses/by/3.0">CC BY 3.0</a>';
 
 var stylesNonMapbox = {
     'open-street-map': {
@@ -91,7 +92,7 @@ var stylesNonMapbox = {
                 type: 'raster',
                 attribution: [
                     OSM,
-                    'Map tiles by <a href="https://stamen.com">Stamen Design</a>, under <a href="https://creativecommons.org/licenses/by/3.0">CC BY 3.0</a>'
+                    stamen
                 ].join(', '),
                 tiles: ['https://stamen-tiles.a.ssl.fastly.net/terrain/{z}/{x}/{y}.png'],
                 tileSize: 256
@@ -113,7 +114,7 @@ var stylesNonMapbox = {
                 type: 'raster',
                 attribution: [
                     OSM,
-                    'Map tiles by <a href="https://stamen.com">Stamen Design</a>, under <a href="https://creativecommons.org/licenses/by/3.0">CC BY 3.0</a>'
+                    stamen
                 ].join(', '),
                 tiles: ['https://stamen-tiles.a.ssl.fastly.net/toner/{z}/{x}/{y}.png'],
                 tileSize: 256
@@ -135,7 +136,7 @@ var stylesNonMapbox = {
                 type: 'raster',
                 attribution: [
                     OSM,
-                    'Map tiles by <a href="https://stamen.com">Stamen Design</a>, under <a href="https://creativecommons.org/licenses/by/3.0">CC BY 3.0</a>'
+                    stamen
                 ].join(', '),
                 tiles: ['https://stamen-tiles.a.ssl.fastly.net/watercolor/{z}/{x}/{y}.png'],
                 tileSize: 256