求高手解答一个javascript问题 20
<!DOCTYPEhtml><htmllang="en"><head><metacharset="UTF-8"><title>Document</title><style...
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#a{width: 200px;height: 200px;border-color: red;border:3px solid #ccc;}
</style>
<script type="text/javascript">
var c=document.getElementById("a");
var i=0;
var color=new Array("red","blue","yellow","green");
function to()
{
if(i>color.length-1)
{
i=0;
}
else
{
c.style.borderColor=color[i];
i=i+1;
setTimeout("to()",100);
}
}
</script>
</head>
<body>
<div id="a"></div>
<input type="button" value="点击闪烁" onclick="to()">
</body>
</html>
请问为何点击不会变换颜色 展开
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#a{width: 200px;height: 200px;border-color: red;border:3px solid #ccc;}
</style>
<script type="text/javascript">
var c=document.getElementById("a");
var i=0;
var color=new Array("red","blue","yellow","green");
function to()
{
if(i>color.length-1)
{
i=0;
}
else
{
c.style.borderColor=color[i];
i=i+1;
setTimeout("to()",100);
}
}
</script>
</head>
<body>
<div id="a"></div>
<input type="button" value="点击闪烁" onclick="to()">
</body>
</html>
请问为何点击不会变换颜色 展开
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试了一下，报错：Uncaught TypeError: Cannot read property 'style' of null
C没有加载到，是null…… 可以这么写：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#a{width: 200px;height: 200px;border-color: red;border:3px solid #ccc;}
</style>
<script type="text/javascript">
window.onload = function(){
c=document.getElementById("a");
}
var i=0;
var color=new Array("red","blue","yellow","green");
function to()
{
if(i>color.length-1)
{
i=0;
}
else
{
c.style.borderColor=color[i];
i=i+1;
setTimeout("to()",1000);
}
}
</script>
</head>
<body>
<div id="a"></div>
<input type="button" value="点击闪烁" onclick="to()">
</body>
</html>
上面的代码只能闪烁四次，如果想一直循环，可以这么弄：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#a{width: 200px;height: 200px;border-color: red;border:3px solid #ccc;}
</style>
<script type="text/javascript">
window.onload = function(){
c=document.getElementById("a");
}
var i=0;
var color=new Array("red","blue","yellow","green");
function to()
{
if(i>color.length-1)
{
i=0;
}
c.style.borderColor=color[i];
i=i+1;
setTimeout("to()",1000);
}
</script>
</head>
<body>
<div id="a"></div>
<input type="button" value="点击闪烁" onclick="to()">
</body>
</html>
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把var c=document.getElementById("a");
放到 to()函数里面，页面还没有加载完成，c就创建了，他会一直是null放到to()里面就能实现了
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#a{width: 200px;height: 200px;border-color: red;border:3px solid #ccc;}
</style>
<script type="text/javascript">
var i=0;
var color=new Array("red","blue","yellow","green");
function to()
{
var c=document.getElementById("a");
if(i>color.length-1)
{
i=0;
}
else
{
c.style.borderColor=color[i];
i=i+1;
setTimeout("to()",100);
}
}
</script>
</head>
<body>
<div id="a"></div>
<input type="button" value="点击闪烁" onclick="to()">
</body>
</html>
放到 to()函数里面，页面还没有加载完成，c就创建了，他会一直是null放到to()里面就能实现了
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#a{width: 200px;height: 200px;border-color: red;border:3px solid #ccc;}
</style>
<script type="text/javascript">
var i=0;
var color=new Array("red","blue","yellow","green");
function to()
{
var c=document.getElementById("a");
if(i>color.length-1)
{
i=0;
}
else
{
c.style.borderColor=color[i];
i=i+1;
setTimeout("to()",100);
}
}
</script>
</head>
<body>
<div id="a"></div>
<input type="button" value="点击闪烁" onclick="to()">
</body>
</html>
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<!DOCTYPE HTML>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<title>menu</title>
<style type="text/css">
#a {
width: 200px;
height: 200px;
border-color: red;
border: 3px solid #ccc;
}
</style>
<script type="text/javascript">
var i = 0;
var color = new Array ("red", "blue", "yellow", "green");
function to ()
{
// 放进去，在外面的时候，dom元素还没有加载完毕，无法获取，采纳即可。
var c = document.getElementById ("a");
if (i > color.length - 1)
{
i = 0;
}
else
{
c.style.borderColor = color[i];
i = i + 1;
setTimeout ("to()", 100);
}
}
</script>
</head>
<body>
<div id="a"></div>
<input type="button" value="点击闪烁" onclick="to()">
</body>
</html>
追问
加进去对了，可是不能循环跳动啊，变换一种颜色就挺住了
追答
你是要循环啊？
把setTimeout改为
setInterval
就好了
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