摘要：
function a(i) { return new Promise((resolve, reject) => { setTimeout(() => { console.log(i); resolve() }, 5000 - 1000 * i) }) } async function b() { c 阅读全文
摘要：
<body> <div id="first" style="width: 300px;height: 300px;background-color: #ccc;">1 <div id="second" style="width: 200px;height: 200px;background-colo 阅读全文