<input type="text" id="box" value="       ">

input::selection{
	background: blue;
}
input{
  border: none;
  font-size: 10000px;
  position: absolute;
  padding: 0;
  height: 60%;
  width: 60%;
  left: 20%;
  top: 20%;
}
input:focus{
  outline: none;
}

blue=function(){
  document.getElementById("box").select()
}
window.addEventListener('click',blue)
blue()