<button onclick="document.getElementById('myImage').src='https://img.8i5.net/image/bulboff.gif'">Turn on the light</button>

<img id="myImage" src="https://img.8i5.net/image/bulboff.gif" style="width:100px">

<button onclick="document.getElementById('myImage').src='https://img.8i5.net/image/bulboff.gif'">Turn off the light</button>

JavaScript 更改了标记的src(source) 属性的值：<img>

示例：