Cache result of a very frequently computed value

esm/components/data_layer/base.js

@@ -43,12 +43,19 @@ class BaseDataLayer {
         this.layout_idx = null;
 
         /**
-         * The unique identifier for this layer. Should be unique within this layer.
+         * The unique identifier for this layer. Should be unique within this panel.
          * @public
          * @member {String}
          */
         this.id     = null;
 
+        /**
+         * The fully qualified identifier for the data layer, prefixed by any parent or container elements.
+         * @type {string}
+         * @private
+         */
+        this._base_id = null;
+
         /**
          * @protected
          * @member {Panel}
@@ -749,10 +756,14 @@ class BaseDataLayer {
      * @returns {string} A dot-delimited string of the format <plot>.<panel>.<data_layer>
      */
     getBaseId () {
+        if (this._base_id) {
+            return this._base_id;
+        }
+
         if (this.parent) {
             return `${this.parent_plot.id}.${this.parent.id}.${this.id}`;
         } else {
-            return '';
+            return this.id.toString();
         }
     }
 
@@ -775,6 +786,7 @@ class BaseDataLayer {
      * @returns {BaseDataLayer}
      */
     initialize() {
+        this._base_id = this.getBaseId();
 
         // Append a container group element to house the main data layer group element and the clip path
         const base_id = this.getBaseId();