DataTransfer's dropEffect not working on IE/Edge with not minified version react.js

code exmaple: [Non-minified version](https://jsfiddle.net/sy7eja68/) and [Minified version](https://jsfiddle.net/sy7eja68/1/) Both have the same code, html and js, the only difference is referenced to different version of react.js files. There are three boxes. Dragging the "**drag me**" box will show a "**start**" at the top, then show a "**over**" if it is dragged over either "**normal drop**" or "**drop react**" box, and show a "**end**" with a drop to the two drop boxes. Everything works fine on my Firefox(43.0.1), and the the [Minified version](https://jsfiddle.net/sy7eja68/1/) works fine on my IE 11, and Edge(13). The only thing dose not work is the [Non-minified version](https://jsfiddle.net/sy7eja68/) on IE/Edge. When dragging over the "**drop react**" box, there shows **NO** "over". In the F12 console, I can see lines of "`SCRIPT16389: Unspecified error.`". And with `console.log(ev.dataTransfer)`, I get this result: ``` [object DataTransfer] { dropEffect: <Permission denied>, effectAllowed: "all", files: FileList {...}, items: DataTransferItemList {...}, types: DOMStringList {...} } ``` I thought the `dropEffect` should also be accessible on IE/Edge with non-minified version react.js files?