script.jsvar input = document.getElementById("editable");
input.addEventListener('focus', function(){
this.classList.add('is-focused');
});
input.addEventListener('blur', function(){
this.classList.remove('is-focused');
}); contenteditable という要素を扱うstyle.css[contenteditable] {
outline: 0px solid transparent;
}
[contenteditable]:focus {
outline: 2px solid grey;
}