<style>
        #div {
            width: 300px;
            height: 300px;
            border: 2px solid gray;
            margin: 100px 0 0 200px;
        }
    </style>
    <script>
        window.onload = function () {
            var color = document.getElementById('color');
            var divs = document.getElementById('div');
            color.onchange = function () {
                if (color.value == 0) {
                    divs.style.backgroundColor = 'white'
                    divs.innerHTML = '我是div'
                } else {
                    divs.innerText = '我的背景颜色变成了' + color.value + '色'
                    divs.style.backgroundColor = color.value
                }
            }
        }
    </script>
     <div>
        <span>请选择您喜欢的颜色:</span>
        <select id="color">
            <option value="0">请选择</option>
            <option value="yellow">黄色</option>
            <option value="orange">橘色</option>
            <option value="pink">粉色</option>
            <option value="purple">紫色</option>
        </select>
    </div>
    <div id="div">我是div</div>