document.addEventListener('DOMContentLoaded', function() {
let elm = document.getElementById('js')
let original = elm.innerHTML
setInterval(function() {
let text = original.split(' ')
let newText = text.map(function(word) {
if (Math.random() > 0.5) {
return word.toUpperCase()
} else {
return word.toLowerCase()
}
}).join(' ')
elm.innerHTML = newText
}, 500)
})