Allow .toJSON() function on objects to be used

.travis.yml

@@ -2,9 +2,10 @@ language: node_js
 node_js:
   - "4"
   - "6"
+  - "8"
 script:
   - >
-    if [ "$TRAVIS_EVENT_TYPE" == "cron" ] && node --version | grep v6\. ; then
+    if [ "$TRAVIS_EVENT_TYPE" == "cron" ] && node --version | grep --invert-match v4\. ; then
       ./bin/build.sh test:live;
     else
       echo "skipping live tests";

lib/database/store.js

@@ -171,6 +171,10 @@ class DataNode {
       return new DataNode({'.value': value, '.priority': priority});
     }
 
+    if (typeof value === 'object' && typeof value.toJSON === 'function') {
+      return this.from(value.toJSON(), priority, now);
+    }
+
     if (!isObject(value) && !Array.isArray(value)) {
       throw new Error(`Invalid data node type: ${value} (${typeof value})`);
     }

test/spec/lib/database/store.js

@@ -62,7 +62,41 @@ describe('store', function() {
     });
   });
 
-  [new Date(), /foo/].forEach(function(v) {
+  it('should let .toJSON() be used as value', function() {
+    class Something {
+      constructor() {
+        Object.defineProperty(this, 'key', {value: 'definedValue', enumberable: false});
+        Object.defineProperty(this, 'key2', {value: 'definedValue'});
+      }
+      toJSON() {
+        return {key: 'val'};
+      }
+    }
+
+    expect(store.create(new Something()).$value()).to.eql({key: 'val'});
+    expect(store.create({v: new Something()}).$value()).to.eql({v: {key: 'val'}});
+  });
+
+  it('should not let classes without .toJSON() be used as value', function() {
+    class Something {
+      constructor() {
+        Object.defineProperty(this, 'key', {value: 'definedValue', enumberable: false});
+        Object.defineProperty(this, 'key2', {value: 'definedValue'});
+      }
+    }
+
+    expect(() => store.create(new Something())).to.throw();
+    expect(() => store.create({v: new Something()})).to.throw();
+  });
+
+  [new Date()].forEach(function(v) {
+    it(`should let ${v.constructor.name} be used as value`, function() {
+      expect(store.create(v).$value()).to.eql(v.toJSON());
+      expect(store.create({v}).$value()).to.eql({v: v.toJSON()});
+    });
+  });
+
+  [/foo/].forEach(function(v) {
     it(`should not let ${v.constructor.name} be used as value`, function() {
       expect(() => store.create(v)).to.throw();
       expect(() => store.create({v})).to.throw();

test/spec/lib/util.js

@@ -8,9 +8,15 @@ describe('util', function() {
 
   describe('setFirebaseData', function() {
 
-    it('should throw on invalid data', function() {
+    it('should not throw on invalid data', function() {
       expect(
         () => util.setFirebaseData(new Date())
+      ).to.not.throw();
+    });
+
+    it('should throw on invalid data', function() {
+      expect(
+        () => util.setFirebaseData(/regex/)
       ).to.throw();
     });