I was trying to fix this warning:
Warning: Each child in an array or iterator should have a unique "key" prop. Check the render method of Text. See http://fb.me/react-warning-keys for more information.
After some searching I ended up in react.js, where I found (in ReactElement.createElement):
key = config.code === undefined ? null : '' + config.code;
I finally managed to get rid of the warning by using React.createElement("li", {code: ...}) instead of React.createElement("li", {key: ...}).
This should be fixed, probably in .createElement, or at least in the docs/warning.