How can I add properties to a react component passed as a variable?

Question

My scenario is that I'm creating a render() function in a controller (not React related) to render views with the option of specifying a layout. That way I can have multiple different layout components, all accepting a content property, that can be rendered in a simple way. Here's what I'm trying to do in a nutshell:

render: function(content, layout) {
    layout = layout || <Layout />;
    layout.setProps({ content: content });
    React.render(layout, document.body);
}

Can it be done? Or if you think it can be done but it's a bad idea, please let me know why.

Answer 1

There are a couple ways you could approach this.

The simplest is to pass the layout's type and properties separately:

function render(content, layoutType, layoutProperties) {
  layoutType = layoutType || Layout;
  layoutProperties = layoutProperties || {};

  var props = { content: content };
  for (var key in layoutProperties) {
    props[key] = layoutProperties[key];
  }

  var layout = React.createElement(layoutType, props);

  React.render(layout, document.body);
}

render(<div>Test 1</div>);
render(<div>Test 2</div>, CustomLayout, { title: "Test Title" });

^{JSFiddle example: http://jsfiddle.net/BinaryMuse/hjLufbkz/}

If you want to pass a fully-realized ReactElement as the layout instead, you could use React.addons.cloneWithProps (or, in v0.13 RC2 and later, React.cloneElement):

function render(content, layout) {
  var props = { content: content };
  layout = layout || <Layout />;
  layout = React.addons.cloneWithProps(layout, props);

  React.render(layout, document.body);
}

render(<div>Test 1</div>);
render(<div>Test 2</div>, <CustomLayout title="Test Title" />);

^{JSFiddle example: http://jsfiddle.net/BinaryMuse/8krawhx4/}

---

I'm a big fan of using this.props.children to nest elements; note that you can modify both the techniques above to do so:

function render(content, layoutType, layoutProperties) {
  layoutType = layoutType || Layout;
  layoutProperties = layoutProperties || {};

  var layout = React.createElement(layoutType, layoutProperties, content);

  React.render(layout, document.body);
}

^{JSFiddle example: http://jsfiddle.net/BinaryMuse/6g8uyfp4/}

and

function render(content, layout) {
  layout = layout || <Layout>{content}</Layout>;
  layout = React.addons.cloneWithProps(layout, {children: content});

  React.render(layout, document.body);
}

^{JSFiddle example: http://jsfiddle.net/BinaryMuse/nadv297h/}

Of course, if one of your custom layout components already utilizes this.props.children for other purposes, the original technique with cloneWithProps/cloneElement and this.props.content works just fine. (JSFiddle example: http://jsfiddle.net/BinaryMuse/b5ncfnqh/)