Javascript - Select div 元素按其 class 名称并在其中添加图像

Question

 let output = document.getElementsByClassName("one"); const img = document.createElement("img"); img.src = "https://www.gravatar.com/avatar/4581a99fa5793feaeff38d989a1524c6?s=48&d=identicon&r=PG"; img.width = "25px"; document.output[0].appendChild(img);

 .one { border: 2px solid red; }

 <div class="one">Test</div>

上面的代码给出了一个错误Uncaught TypeError: Cannot read properties of undefined (reading '0') ...

Answer 1

您需要参考output[0] ，而不是document.output[0] 。

此外，您需要将图像width=""属性设置为25 ，而不是25px 。

 let output = document.getElementsByClassName("one"); const img = document.createElement("img"); img.src = "https://www.gravatar.com/avatar/4581a99fa5793feaeff38d989a1524c6?s=48&d=identicon&r=PG"; img.width = "25"; output[0].appendChild(img);

 .one { border: 2px solid red; }

 <div class="one">Test</div>