44、用按钮来调整网页背景色

44、用按钮来调整网页背景色

要完成此效果需要两个步骤

 

第一步:把如下代码加入到<head>区域中

 

<SCRIPT LANGUAGE="JavaScript">

<!-- Begin

function color(frm, clr, val) {

v = eval("0x" + frm[clr].value) + val;

if (v < 0 || v > 255) v -= val;

v = v.toString(16).toUpperCase();

while (v.length < 2) v = "0" + v;

frm[clr].value = v; nc = "";

for(i = 1; i < 8; i += 3) nc += frm.elements[i].value;

document.bgColor = nc;

}

function setval(item) {

v = prompt("请输入颜色代码 " + item.name + " (00 - FF)", item.value);

if (v) {

v = eval("0x" + v);

if ((v & 255) == v) {

item.value=v.toString(16).toUpperCase();

while (item.value.length < 2) item.value = "0" + item.value;

color(document.f, item.name, 0);

      }

   }

}

//  End -->

</script>

 

 

第二步:把如下代码加入到<body>区域中

 

<center>

<form name=f>

<table border=1>

<tr>

<td colspan=3 align=center bgcolor="#ff0000">RED</td>

<td colspan=3 align=center bgcolor="#00ff00">GREEN</td>

<td colspan=3 align=center bgcolor="#000ff">BLUE</td>

</tr>

<tr>

<td><input type=button name=rm value="<" onclick = "color(this.form, 'Red' , -1);"></td>

<td><input type=button name=Red value="AF" onclick = "setval(this);"></td>

<td><input type=button name=rp value=">" onclick = "color(this.form, 'Red', 1);"></td>

<td><input type=button name=gm value="<" onclick = "color(this.form, 'Green', -1);"></td>

<td><input type=button name=Green value="BF" onclick = "setval(this);"></td>

<td><input type=button name=gp value=">" onclick = "color(this.form, 'Green', 1);"></td>

<td><input type=button name=bm value="<" onclick = "color(this.form, 'Blue', -1);"></td>

<td><input type=button name=Blue value="CF" onclick = "setval(this);"></td>

<td><input type=button name=bp value=">" onclick = "color(this.form, 'Blue', 1);"></td>

</tr>

</table>

</form>

</center>

 

 

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