CODE EXAMPLE FOR JAVASCRIPT

change react native app name

android:
android/app/src/main/res/values/string.xml > change APP_NAME.

ios:
ios/[currentName].xcodeproj/project.pbxproj > change PRODUCT_NAME in debug and release. 
or
go to ios/[currentName]/info.plist
<key>CFBundleDisplayName</key>
<string>${PRODUCT_NAME}</string>