innerHTML innerText
<div></div>
<script>
    var div=document.getElementsByTagName('div');
    console.log(div[0]);
    div[0].innerText='today is Monday';
    // for (let i=0;i<5**8;i++);
    div[0].innerHTML='today is <strong>Monday</strong>' +
        '<span>.</span>';
    console.log(div[0].innerHTML);
    console.log(div[0].innerText);
</script>

前者保留<strong>等表示,后者只显示文本,且如有换行则去掉换行