How do I make if statement to accept both upper and lower case letters

Question

document.querySelector(`#check`).addEventListener('click', check)


function check() {
  const day = document.querySelector(`#day`).value

  if (day === 'Saturday' || day === 'Sunday') {
    document.querySelector('#placeToSee').innerHTML = 'Weekend'
  } else if (day === 'Tuesday ' || day === 'Thursday') {
    document.querySelector('#placeToSee').innerHTML = 'Schoolday'
  } else {
    document.querySelector('#placeToSee').innerHTML = 'Boring'
  }
}

I am trying to make the code accept Lowercase and uppercase Tuesday or Sunday as the case maybe in JavaScript if statements. I have tried all I know and I am just starting out in Learning JavaScript