select + option

可以实现一个下拉选择，选择到那个，就可以获取其value，并且弹窗。

<!DOCTYPE HTML>
<html>
        <head>
        	<meta charset="utf-8">
      	<style>
		.sty1{background-color:#aaa;height:200px;width:200px;margin-top:20px;float:left;margin-left:10px;}
	</style>
        </head>
        <body>
     	<div id = "div1" class = "sty1" ></div>
	<div id = "div2" class = "sty1"></div>
	<div id = "div3" class = "sty1" ></div>
	<select id = "s1" onchange = "m1()">
		<option value="flag0">请选择样式</option>
		<option value="flag1">样式1</option>
		<option value="flag2">样式2</option>
		<option value="flag3">样式3</option>
		<option value="flag4">样式4</option>
		<option value="flag5">样式5</option>
	<select>
         </body>
         <script>
	function m1(){
		var x = document.getElementById("s1");
		alert(x.value);
	}
	function m2(){
		
	}
         </script>

    </html>

这样我们就可以根据获取到的不同value，做出不同的动作如：

	function m1(){
		var x = document.getElementById("s1");
		var x1 =  document.getElementById("div1");
		var x2 =  document.getElementById("div2");
		var x3 =  document.getElementById("div3");
		alert(x.value);
		if (x.value == "flag1"){
			x1.style.backgroundColor = "#a00";
		}else if (x.value == "flag2"){
			x2.style.width = "300px";
		}else if (x.value == "flag3"){
			x3.style.opacity = "0.5";
		}
		
	}

在这里插入图片描述

innerHTML 在元素中插入内容

注意： 最好用单引号’来表示，以防和其中的"冲突，当然也可用\掉"，但是太麻烦了。
如：

		var x1 =  document.getElementById("div1");
		if (x.value == "flag1"){
			x1.innerHTML = "大家好";

当我们选择标签1的时候在div1中插入文字"大家好"
在这里插入图片描述
当然不止可以放文本，还可以放入其他元素比如我们这里放入几个小方块嵌套在其中。

<!DOCTYPE HTML>
<html>
        <head>
        	<meta charset="utf-8">
      	<style>
		.sty1{background-color:#aaa;height:200px;width:200px;margin-top:20px;float:left;margin-left:10px;}
	</style>
        </head>
        <body>
     	<div id = "div1" class = "sty1" ></div>
	<div id = "div2" class = "sty1"></div>
	<div id = "div3" class = "sty1" ></div>
	<select id = "s1" onchange = "m1()">
		<option value="flag0">请选择样式</option>
		<option value="flag1">样式1</option>
		<option value="flag2">样式2</option>
		<option value="flag3">样式3</option>
		<option value="flag4">样式4</option>
		<option value="flag5">样式5</option>
	<select>
         </body>
         <script>
	function m1(){
		var x = document.getElementById("s1");
		var b1 =  document.getElementById("div1");
		var x2 =  document.getElementById("div2");
		var x3 =  document.getElementById("div3");
		//alert(x.value);
		if (x.value == "flag1"){
			b1.backgroundColor = "#2ac";
			
			var html = ' ';
			
			for (var i = 0; i < 10; i++){
				html += '<div style = "height:40px;width:40px;background-color:#2ac;float:left;margin-left:10px;margin-top:10px;"></div>';
			}
			b1.innerHTML = html;
			
		}

		
	}
	function m2(){
		
	}
         </script>

    </html>