React Native foreach loop

You can use map or for-of or any other

Example:

// for of
for (let userObject of this.state.users) {
    console.log(userObject.username);
}
// map
this.state.users.map((userData) => {
    console.log(userData.username);
});

as per the error you may not have data within users state, so you are getting error. If data is proper then above example will work properly

In react, preferred way is map method of Array. Example using ES6 arrow function:

render() {    
    return (
        <View>    
           {dataList.map(r => <Button>{r}</Button>)}    
        </View>
    )
}