var $ = 'jQuery'

​

var result = (function(){

  var $ = false

  var whatever = 'hi'

  return Math.random() >= 0.5 ? true : false

})()

​

document.querySelector('button').onclick = function(){

  alert('$ is '+ $)

  alert('result is '+result)

  alert(whatever) // Uncaught ReferenceError: whatever is not defined 

}

​

​