Merge pull request facebook#2583 from spicyj/style-example

Add example for how to use `style` properly

Author: sophiebits

src/browser/ui/ReactDOMComponent.js

@@ -69,7 +69,8 @@ function assertValidProps(props) {
   invariant(
     props.style == null || typeof props.style === 'object',
     'The `style` prop expects a mapping from style properties to values, ' +
-    'not a string.'
+    'not a string. For example, style={{marginRight: spacing + \'em\'}} when ' +
+    'using JSX.'
   );
 }
 

src/browser/ui/__tests__/ReactDOMComponent-test.js

@@ -353,7 +353,8 @@ describe('ReactDOMComponent', function() {
         mountComponent({ style: 'display: none' });
       }).toThrow(
         'Invariant Violation: The `style` prop expects a mapping from style ' +
-        'properties to values, not a string.'
+        'properties to values, not a string. For example, ' +
+        'style={{marginRight: spacing + \'em\'}} when using JSX.'
       );
     });
   });
@@ -398,7 +399,8 @@ describe('ReactDOMComponent', function() {
         React.render(<div style={1}></div>, container);
       }).toThrow(
         'Invariant Violation: The `style` prop expects a mapping from style ' +
-        'properties to values, not a string.'
+        'properties to values, not a string. For example, ' +
+        'style={{marginRight: spacing + \'em\'}} when using JSX.'
       );
     });
   });