console 命令行工具 X clear
console
<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title class="lang" key="title"></title>
</head>

<body style="padding: 50px">
    <h2 class="lang" key="hello"></h2>
    <p class="lang" key="name"></p>
    <div>
        <button class="lang" key="switch1" onclick=document.children[0].setAttribute('lang','en')></button>
        <button class="lang" key="switch2" onclick=document.children[0].setAttribute('lang','zh-CN')></button>
    </div>
</body>

<script>
    let langPackage = {
        'en': {
            hello: 'Hello',
            name: 'Nowell',
            title: 'title',
            switch1: 'english',
            switch2: 'chinese'
        },
        'zh-CN': {
            hello: '你好',
            name: '小杨',
            title: '标题',
            switch1: '英文',
            switch2: '中文'
        }
    }

    let changeLang = () => {
        let lang = document.children[0].lang || 'en'
        Array.from(document.getElementsByClassName('lang')).forEach((el, index) => {
            let key = el.getAttribute('key')
            el.innerText = langPackage[lang][key]
        })
    }
    // 使用mutationObserver来观察dom的变化， 此处只观察属性值的变化
    let mutationObserver = new MutationObserver((mutationList, observer) => changeLang())
    mutationObserver.observe(document.children[0], { attributes: true })
    window.addEventListener('DOMContentLoaded', changeLang)

</script>

</html>