测试
请打开console查看结果
function sayHello(){
console.log('hello')
}
sayHello()
button
<div id="btn">button</div>
<style>
#btn{
width: 20px;
height: 20px;
background: red;
}
</style>
<script>
function btnSayHello(){
console.log('hello btn')
}
document.getElementById('btn').onclick = btnSayHello
</script>
type A = string;