<input type="number" id="study" name="box" />
<button onclick="guess()">猜</button>
<button onclick="setRandom()">产生随机数</button>
let study = document.getElementById('study')
let randomNum;
function guess() {
console.log(randomNum )
if(!randomNum ) return alert('还未生成随机数')
let num = Number(study.value);
if(num === randomNum){ alert('猜对了') }
else if(num < randomNum){alert('猜小了')}else{alert('猜大了')}
}
function setRandom(){
randomNum=Math.ceil(Math.random()*100);
}