Add Accessing Env Vars In create-react-app as a react til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
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-_582 TILs and counting..._
+_583 TILs and counting..._
 
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@@ -409,6 +409,7 @@ _582 TILs and counting..._
 
 ### React
 
+- [Accessing Env Vars In create-react-app](react/accessing-env-vars-in-create-react-app.md)
 - [Force A Component To Only Have One Child](react/force-a-component-to-only-have-one-child.md)
 - [Inline Style Attributes Should Be Camel Cased](react/inline-style-attributes-should-be-camel-cased.md)
 - [Passing Props Down To React-Router Route](react/passing-props-down-to-react-router-route.md)

react/accessing-env-vars-in-create-react-app.md

@@ -0,0 +1,27 @@
+# Access Env Vars In create-react-app
+
+Environment-specific configurations are an important part of most
+applications. You can access environment variables in your create-react-app
+code using `process.env`.
+
+There are a couple built-in environment variables, such as `NODE_ENV`.
+Anything custom that you want to provide must be prepended with
+`REACT_APP_`. If it isn't, that environment variable will be ignored with no
+warning.
+
+The following line of code
+
+```javascript
+const base_api_url = process.env.REACT_APP_BASE_API_URL;
+```
+
+will have access to whatever that value is in the environment when the
+server is started or the app is built.
+
+Set that value inline like so:
+
+```
+REACT_APP_BASE_API_URL="https://api.my_app.com" yarn start
+```
+
+[source](https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.md#adding-custom-environment-variables)