console 命令行工具 X clear

console

function setColor(color){
			var oDiv1=document.getElementById('div1');
			oDiv1.style.background=color;
			//等同oDiv1.style[background]=color;方括号用于[]里面的值不确定
		}

		function setStyle(name,value){
			var oDiv2=document.getElementById('div2');
			oDiv2.style[name]=value;
		}

		function toRed(){
			var oDiv3=document.getElementById('div3');
			oDiv3.style.background='red';
		}

		// window.onload=function(){
		// 	var oDiv4=document.getElementsByTagName('div4');
		// 	oDiv4[0].style.background='red';
		// }

		window.onload=function(){
			var oBtn1=document.getElementById('btn1');
			var oBtn2=document.getElementById('btn2');
			var oBtn3=document.getElementById('btn3');
			var oDivc=document.getElementById('divc');
			var aCh=oDivc.getElementsByTagName('input');

			oBtn1.onclick=function(){
				for(var i=0;i<aCh.length;i++){
					aCh[i].checked=true;
				}
			};

			oBtn2.onclick=function(){
				for(var i=0;i<aCh.length;i++){
					aCh[i].checked=false;
				}
			};

			oBtn3.onclick=function(){
				for(var i=0;i<aCh.length;i++){

					if (aCh[i].checked==true) {
						aCh[i].checked=false;
					}
					else{
						aCh[i].checked=true;
					}
					
				}
			};
		};

<body>
	<input type="button" value="变红" onclick="setColor('red')">
	<input type="button" value="变绿" onclick="setColor('green')">
	<input type="button" value="变黄" onclick="setColor('yellow')">
	<div id="div1"></div>	
	<br>

	<input type="button" value="变宽" onclick="setStyle('width','400px')">
	<input type="button" value="变高" onclick="setStyle('height','400px')">
	<input type="button" value="变蓝" onclick="setStyle('background','blue')">
	<div id="div2"></div>
	<br>

	<input type="button" value="变红" onclick="toRed()">
	<div id="div3"></div>
	<br>

	<input id="btn1" type="button" value="全选">
	<input id="btn2" type="button" value="不选">
	<input id="btn3" type="button" value="反选"><br>
	<div id="divc">
		<input type="checkbox"><br>
		<input type="checkbox"><br>
		<input type="checkbox"><br>
	</div>
	
</body>

#div1{
			width: 200px;
			height: 200px;
			background: grey;
		}
		#div2{
			width: 200px;
			height: 200px;
			background:pink;
		}
		#div3{
			width: 200px;
			height: 200px;
			border:1px solid black;	
		}