<script>
    document.getElementById('add-Box').addEventListener('click', function (event) {
        let itemParent = document.getElementById('box-Parent');
        let newItem = document.createElement('li');
        newItem.className = 'box';
        itemParent.appendChild(newItem);
    })
</script>

如果你想在一个方法中创建多个元素。

function createElement(el, options, listen = [], appendTo){ let element = document.createElement(el); Object.keys(options).forEach(function (k){ element[k] = options[k]; }); if(listen.length > 0){ listen.forEach(function(l){ element.addEventListener(l.event, l.f); }); } appendTo.append(element); } let main = document.getElementById('addHere'); createElement('button', {id: 'myBtn', className: 'btn btn-primary', textContent: 'Add Alert'}, [{ event: 'click', f: function(){ createElement('div', {className: 'alert alert-success mt-2', textContent: 'Working' }, [], main); } }], main); <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.6.0/dist/css/bootstrap.min.css" integrity="sha384-B0vP5xmATw1+K9KRQjQERJvTumQW0nPEzvF6L/Z6nronJ3oUOFUFpCjEUQouq2+l" crossorigin="anonymous"> <div id="addHere" class="text-center mt-2"></div>

同样值得一看的是:

var el = document.getElementById('hello');
if(el) {
    el.className += el.className ? ' someClass' : 'someClass';
}

使用.classList.add()方法:

const element = document.querySelector('div.foo'); element.classList.add('酒吧'); console.log (element.className); < div class = " foo " > < / div >

这个方法比覆盖className属性更好，因为它不会删除其他类，如果元素已经有该类，也不会添加该类。

您还可以使用element切换或删除类。classList(参见MDN文档)。

如果你想创建一个新的输入字段，例如文件类型:

 // Create a new Input with type file and id='file-input'
 var newFileInput = document.createElement('input');

 // The new input file will have type 'file'
 newFileInput.type = "file";

 // The new input file will have class="w-95 mb-1" (width - 95%, margin-bottom: .25rem)
 newFileInput.className = "w-95 mb-1"

输出为:<input type="file" class="w-95 mb-1">

如果你想用JavaScript创建一个嵌套的标签，最简单的方法是使用innerHtml:

var tag = document.createElement("li");
tag.innerHTML = '<span class="toggle">Jan</span>';

输出将是:

<li>
    <span class="toggle">Jan</span>
</li>

var newItem = document.createElement('div');
newItem.style = ('background-color:red'); 
newItem.className = ('new_class');
newItem.innerHTML = ('<img src="./profitly_files/TimCover1_bigger.jpg" width=50 height=50> some long text with ticker $DDSSD');
var list = document.getElementById('x-auto-1');
list.insertBefore(newItem, list.childNodes[0]);