Question: I'm looking to use React Native for app development. Since it is free and an open source, cross-platform environment. The question is: what IDE can I use to write and build and do everything in it?
Appreciate the help.

Answer: 
Since I use their IDEs for other languages too I use PhpStore/WebStorm from JetBrains. It's a very good set of tools. As an added bonus Android Studio is using the JetBrains IDE as a basis as well. So you'll feel right at home there. On the downside you have to pay and they just this month switch over to a subscription model. But as a professional developer I'm willing to pay for tools that make me more productive.
Windows I use sublime text3 as IDE,Plugin:

`ReactJS: support React development, code hints, highlighting`

`Emmet: front-end development necessary.`

`Terminal: open the terminal in sublime and navigate to the current directory, artifacts, mac shortcut keys: command + shift + T`

`React-native-snippets: react native snippet`

The following options, to solve the grammar check error

> 
> Open the menu `view`, `Syntax` -> `Open all with current extension as ...` -> `Babel` -> `JavaScript (Babel)`, select babel as the default javascript open syntax
>  Be sure to choose Open all with current extension as ... .
> 
> 
> 

Mac I use Atom ,Plugin:Nuclide