var tweets = [
  {tweet: "hello", name: "jesstelford"},
  {tweet: "hi", name: "taylorswift"},
  {tweet: "g'day", name: "bigbird"}
]

function makeTweet(tweetData) {
  return tweetData.tweet + ' by @' + tweetData.name
}

var theTweets = tweets.map(makeTweet).join('<br>')
document.querySelector('section').innerHTML = theTweets