ReactJs: How to pass the initial state while rendering a component?

Question

I know I can pass props while rendering a component. I'm also aware of the getInitialState method. But the problem is, getInitialState isn't quite helping because my component doesn't know it's initial state. I do. So I want to pass it while I'm rendering it.

Something like this (pseudo-code):

React.render(<Component initialState={...} />);

I know I could use a prop to work as the initial state but this smells like an anti-pattern.

What should I do?

EDIT FOR CLARITY

Imagine I have a CommentList component. By the time I first render it, the initial state corresponds to the snapshot of current comments from my database. As the user includes comments, this list will change, and that's why it should be a state and not props. Now, in order to render the initial snapshot of comments I should pass it to the CommentsList component, because it has no way to know it. My confusion is that the only way I see to pass this information is through a props which seems to be an anti-pattern.

Answer 1

Disclaimer: Newer versions of React handle this on a different way.

Only permanent components might be able to use props in the getInitialState. Props in getInitialState is an anti-pattern if synchronization is your goal. getInitialState is only called when the component is first created so it may raise some bugs because the source of truth is not unique. Check this answer.

Quoting documentation:

Using props, passed down from parent, to generate state in getInitialState often leads to duplication of "source of truth", i.e. where the real data is. Whenever possible, compute values on-the-fly to ensure that they don't get out of sync later on and cause maintenance trouble

You can still do:

getInitialState: function() {
   return {foo: this.props.foo}
}

As they will be the default props for your app. But as long as you are using a prop to set a value that presumably won't change, you can use the same prop inside of the render function.

<span>{this.props.foo}</span>

This props won't be modified, so no problem using it each time the render is called.

Edited answer:

In this case your initial state should not be a prop, should be an ajax call which populates the comment list.