Creating an object that stores properties only when needed in BaseObject class

src/ol/Feature.js

@@ -128,7 +128,9 @@ class Feature extends BaseObject {
    * @api
    */
   clone() {
-    const clone = new Feature(this.getProperties());
+    const clone = new Feature(
+      this.hasProperties() ? this.getProperties() : undefined
+    );
     clone.setGeometryName(this.getGeometryName());
     const geometry = this.getGeometry();
     if (geometry) {

src/ol/Object.js

@@ -4,7 +4,7 @@
 import Event from './events/Event.js';
 import ObjectEventType from './ObjectEventType.js';
 import Observable from './Observable.js';
-import {assign} from './obj.js';
+import {assign, isEmpty} from './obj.js';
 import {getUid} from './util.js';
 
 /**
@@ -94,10 +94,10 @@ class BaseObject extends Observable {
     getUid(this);
 
     /**
+     * @name values_
      * @private
      * @type {!Object<string, *>}
      */
-    this.values_ = {};
 
     if (opt_values !== undefined) {
       this.setProperties(opt_values);
@@ -112,7 +112,7 @@ class BaseObject extends Observable {
    */
   get(key) {
     let value;
-    if (this.values_.hasOwnProperty(key)) {
+    if (this.values_ && this.values_.hasOwnProperty(key)) {
       value = this.values_[key];
     }
     return value;
@@ -124,7 +124,7 @@ class BaseObject extends Observable {
    * @api
    */
   getKeys() {
-    return Object.keys(this.values_);
+    return (this.values_ && Object.keys(this.values_)) || [];
   }
 
   /**
@@ -133,7 +133,14 @@ class BaseObject extends Observable {
    * @api
    */
   getProperties() {
-    return assign({}, this.values_);
+    return (this.values_ && assign({}, this.values_)) || {};
+  }
+
+  /**
+   * @return {boolean} The object has properties.
+   */
+  hasProperties() {
+    return !!this.values_;
   }
 
   /**
@@ -156,11 +163,12 @@ class BaseObject extends Observable {
    * @api
    */
   set(key, value, opt_silent) {
+    const values = this.values_ || (this.values_ = {});
     if (opt_silent) {
-      this.values_[key] = value;
+      values[key] = value;
     } else {
-      const oldValue = this.values_[key];
-      this.values_[key] = value;
+      const oldValue = values[key];
+      values[key] = value;
       if (oldValue !== value) {
         this.notify(key, oldValue);
       }
@@ -187,9 +195,12 @@ class BaseObject extends Observable {
    * @api
    */
   unset(key, opt_silent) {
-    if (key in this.values_) {
+    if (this.values_ && key in this.values_) {
       const oldValue = this.values_[key];
       delete this.values_[key];
+      if (isEmpty(this.values_)) {
+        delete this.values_;
+      }
       if (!opt_silent) {
         this.notify(key, oldValue);
       }

src/ol/format/EsriJSON.js

@@ -199,6 +199,11 @@ class EsriJSON extends JSONFeature {
   writeFeatureObject(feature, opt_options) {
     opt_options = this.adaptOptions(opt_options);
     const object = {};
+    if (!feature.hasProperties()) {
+      object['attributes'] = {};
+      return object;
+    }
+    const properties = feature.getProperties();
     const geometry = feature.getGeometry();
     if (geometry) {
       object['geometry'] = writeGeometry(geometry, opt_options);
@@ -214,9 +219,8 @@ class EsriJSON extends JSONFeature {
           ),
         });
       }
+      delete properties[feature.getGeometryName()];
     }
-    const properties = feature.getProperties();
-    delete properties[feature.getGeometryName()];
     if (!isEmpty(properties)) {
       object['attributes'] = properties;
     } else {

src/ol/format/GML2.js

@@ -212,29 +212,32 @@ class GML2 extends GMLBase {
       context.serializers = {};
       context.serializers[featureNS] = {};
     }
-    const properties = feature.getProperties();
     const keys = [];
     const values = [];
-    for (const key in properties) {
-      const value = properties[key];
-      if (value !== null) {
-        keys.push(key);
-        values.push(value);
-        if (
-          key == geometryName ||
-          typeof (/** @type {?} */ (value).getSimplifiedGeometry) === 'function'
-        ) {
-          if (!(key in context.serializers[featureNS])) {
-            context.serializers[featureNS][key] = makeChildAppender(
-              this.writeGeometryElement,
-              this
-            );
-          }
-        } else {
-          if (!(key in context.serializers[featureNS])) {
-            context.serializers[featureNS][key] = makeChildAppender(
-              writeStringTextNode
-            );
+    if (feature.hasProperties()) {
+      const properties = feature.getProperties();
+      for (const key in properties) {
+        const value = properties[key];
+        if (value !== null) {
+          keys.push(key);
+          values.push(value);
+          if (
+            key == geometryName ||
+            typeof (/** @type {?} */ (value).getSimplifiedGeometry) ===
+              'function'
+          ) {
+            if (!(key in context.serializers[featureNS])) {
+              context.serializers[featureNS][key] = makeChildAppender(
+                this.writeGeometryElement,
+                this
+              );
+            }
+          } else {
+            if (!(key in context.serializers[featureNS])) {
+              context.serializers[featureNS][key] = makeChildAppender(
+                writeStringTextNode
+              );
+            }
           }
         }
       }

src/ol/format/GML3.js

@@ -843,29 +843,32 @@ class GML3 extends GMLBase {
       context.serializers = {};
       context.serializers[featureNS] = {};
     }
-    const properties = feature.getProperties();
     const keys = [];
     const values = [];
-    for (const key in properties) {
-      const value = properties[key];
-      if (value !== null) {
-        keys.push(key);
-        values.push(value);
-        if (
-          key == geometryName ||
-          typeof (/** @type {?} */ (value).getSimplifiedGeometry) === 'function'
-        ) {
-          if (!(key in context.serializers[featureNS])) {
-            context.serializers[featureNS][key] = makeChildAppender(
-              this.writeGeometryElement,
-              this
-            );
-          }
-        } else {
-          if (!(key in context.serializers[featureNS])) {
-            context.serializers[featureNS][key] = makeChildAppender(
-              writeStringTextNode
-            );
+    if (feature.hasProperties()) {
+      const properties = feature.getProperties();
+      for (const key in properties) {
+        const value = properties[key];
+        if (value !== null) {
+          keys.push(key);
+          values.push(value);
+          if (
+            key == geometryName ||
+            typeof (/** @type {?} */ (value).getSimplifiedGeometry) ===
+              'function'
+          ) {
+            if (!(key in context.serializers[featureNS])) {
+              context.serializers[featureNS][key] = makeChildAppender(
+                this.writeGeometryElement,
+                this
+              );
+            }
+          } else {
+            if (!(key in context.serializers[featureNS])) {
+              context.serializers[featureNS][key] = makeChildAppender(
+                writeStringTextNode
+              );
+            }
           }
         }
       }

src/ol/format/GeoJSON.js

@@ -207,16 +207,22 @@ class GeoJSON extends JSONFeature {
       object.id = id;
     }
 
-    const geometry = feature.getGeometry();
-    if (geometry) {
-      object.geometry = writeGeometry(geometry, opt_options);
+    if (!feature.hasProperties()) {
+      return object;
     }
 
     const properties = feature.getProperties();
-    delete properties[feature.getGeometryName()];
+    const geometry = feature.getGeometry();
+    if (geometry) {
+      object.geometry = writeGeometry(geometry, opt_options);
+
+      delete properties[feature.getGeometryName()];
+    }
+
     if (!isEmpty(properties)) {
       object.properties = properties;
     }
+
     return object;
   }