Javascript 检查子元素是否没有特定的类？

我试图找出子元素是否没有特定的类

我的要点如下：

<g id="note1">
    <path id="Barline1" d="M55.837,19.278h0.249c0.11,0,0.199,0.089,0.199,0.199V40.56c0,0.11-0.089,0.199-0.199,0.199h-0.249c-0.11,0-0.199-0.089-0.199-0.199V19.478C55.638,19.368,55.727,19.278,55.837,19.278z"/>
    <path class="root" d="M54.113,38.945c1.116,0,2.172,0.578,2.172,1.813c0,1.435-1.116,2.411-2.052,2.969c-0.717,0.418-1.514,0.717-2.331,0.717c-1.116,0-2.172-0.578-2.172-1.813c0-1.435,1.116-2.411,2.052-2.969C52.499,39.244,53.296,38.945,54.113,38.945z"/>
</g>
<g id="note2">
    <path id="BarLine2" d="M70.852,16.788h0.249c0.11,0,0.199,0.089,0.199,0.199v21.082c0,0.11-0.089,0.199-0.199,0.199h-0.249c-0.11,0-0.199-0.089-0.199-0.199V16.987C70.653,16.877,70.742,16.788,70.852,16.788z"/>
    <path class="root" d="M69.127,36.454c1.116,0,2.172,0.578,2.172,1.813c0,1.435-1.116,2.411-2.052,2.969c-0.717,0.418-1.514,0.717-2.331,0.717c-1.116,0-2.172-0.578-2.172-1.813c0-1.435,1.116-2.411,2.052-2.969C67.513,36.753,68.31,36.454,69.127,36.454z"/>
    <path class="interval third" d="M69.127,31.473c1.116,0,2.172,0.578,2.172,1.813c0,1.435-1.116,2.411-2.052,2.969c-0.717,0.418-1.514,0.717-2.331,0.717c-1.116,0-2.172-0.578-2.172-1.813c0-1.435,1.116-2.411,2.052-2.969C67.513,31.772,68.31,31.473,69.127,31.473z"/>
</g>

我收到的错误消息是，两个

g

元素都不支持属性或方法

document.getElementsByClassName

根据，代码应该返回我想要的类的所有元素，这些元素位于我指定的id的元素下。有没有关于我做错了什么或我可能会尝试什么替代方案的想法？

您可以使用：

---

您从

.root

元素开始而不是从

note\uu

元素开始有什么原因吗？可能是无知。这对于检查子元素是否没有类元素非常有效。尽管如此，我不确定现在如何访问子元素，因为它确实有类。是

document.getElementById（'note'+（n+1））.querySelectorAll（'getElementById（'note'+（n+1））[0]

，还是一旦我进入，我就返回到

getElementsByCassName

？@ChristopherGaston:你可以通过迭代节点列表

document.getElementById（'note'+（n+1））.querySelectorAll（'getElementInterval'）

，并使用，第一个你可以访问的方式，你在评论。工作得很好。您可能需要编辑代码。你记下了#interval，它是id选择器，实际上应该是.interval，用于类选择器。

for(var n=0;n<document.getElementsByClassName('root').length;n++){
    if(document.getElementById('note'+(n+1)).getElementsByClassName('interval') ){
          //some child element has class
     } else {
          //no child element has class
     }
}

 if(document.getElementById('note'+(n+1)).querySelectorAll('.interval').length > 0){
     /*There are elements with CSS class 'interval'*/
 }
 else{
     /*There are no elements with CSS class 'interval'*/
 }