Reset textarea to empty after defaultValue is removed or null

This doesn't have an attribute to be removed so we just reset it to empty string.

packages/react-dom-bindings/src/client/ReactDOMTextarea.js

@@ -62,6 +62,11 @@ export function updateTextarea(element: Element, props: Object) {
   const node: HTMLTextAreaElement = (element: any);
   const value = getToStringValue(props.value);
   const defaultValue = getToStringValue(props.defaultValue);
+  if (defaultValue != null) {
+    node.defaultValue = toString(defaultValue);
+  } else {
+    node.defaultValue = '';
+  }
   if (value != null) {
     // Cast `value` to a string to ensure the value is set correctly. While
     // browsers typically do this as necessary, jsdom doesn't.
@@ -74,9 +79,6 @@ export function updateTextarea(element: Element, props: Object) {
       node.defaultValue = newValue;
     }
   }
-  if (defaultValue != null) {
-    node.defaultValue = toString(defaultValue);
-  }
 }
 
 export function postInitTextarea(element: Element, props: Object) {

packages/react-dom/src/__tests__/ReactDOMTextarea-test.js

@@ -736,4 +736,32 @@ describe('ReactDOMTextarea', () => {
       expect(node.value).toBe('foo');
     });
   });
+
+  it('should remove previous `defaultValue`', () => {
+    const container = document.createElement('div');
+    const node = ReactDOM.render(
+      <textarea defaultValue="0" />,
+      container,
+    );
+
+    expect(node.value).toBe('0');
+    expect(node.defaultValue).toBe('0');
+
+    ReactDOM.render(<textarea />, container);
+    expect(node.defaultValue).toBe('');
+  });
+
+  it('should treat `defaultValue={null}` as missing', () => {
+    const container = document.createElement('div');
+    const node = ReactDOM.render(
+      <textarea defaultValue="0" />,
+      container,
+    );
+
+    expect(node.value).toBe('0');
+    expect(node.defaultValue).toBe('0');
+
+    ReactDOM.render(<textarea defaultValue={null} />, container);
+    expect(node.defaultValue).toBe('');
+  });
 });