<button class="btn btn-primary">大</button>
<button class="btn btn-primary">中</button>
<button class="btn btn-primary">小</button>
<p class="">Lorem ipsum dolor, sit amet consectetur adipisicing elit. Veritatis, assumenda.</p>.big{
font-size:60px;
}
.medium{
font-size:40px;
}
.small{
font-size:20px;
}$(document).ready(function(){
$('.btn').click(function(e){
let button = this.textContent;
switch(button){
case '大':
$('p').attr('class','big');
break;
case '中':
$('p').attr('class','medium');
break;
case '小':
$('p').attr('class','small');
break;
}
})
})