Is this a bug report?

Yes

Have you read the Contributing Guidelines?

Yes

Environment

Environment:
OS: macOS High Sierra 10.13.2
Node: 8.9.3
Yarn: 1.3.2
npm: 5.6.0
Watchman: 4.9.0
Xcode: Xcode 9.2 Build version 9C40b
Android Studio: 2.3 AI-162.4069837

Packages: (wanted => installed)
react: 16.0.0 => 16.0.0
react-native: 0.50.3 => 0.50.3

Target Platform: iOS (9.3)

Steps to Reproduce

(Write your steps here:)

1. use react-native init create a react native project
2. call string.padStart function in any render function

class Welcome extends React.Component{
  render(){
    let tmp='abc'.padStart(12,'0');
    return (
      <View style={{flex:1}}>
      </View>
    );
  }
}

Expected Behavior

running correctly.

(Write what you thought would happen.)

Actual Behavior

(Write what happened. Add screenshots!)

'abc'.padStart is undefined

Reproducible Demo

(Paste the link to an example project and exact instructions to reproduce the issue.)