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<title>floatDecimal.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=gb2312">
<script type="text/javascript">
//保留两位小数
//功能：将浮点数四舍五入，取小数点后2位
function toDecimal(x) {
var f = parseFloat(x);
if (isNaN(f)) {
return;
}
f = Math.round(x*100)/100;
return f;
}
//制保留2位小数，如：2，会在2后面补上00.即2.00
function toDecimal2(x) {
var f = parseFloat(x);
if (isNaN(f)) {
return false;
}
var f = Math.round(x*100)/100;
var s = f.toString();
var rs = s.indexOf('.');
if (rs < 0) {
rs = s.length;
s += '.';
}
while (s.length <= rs + 2) {
s += '0';
}
return s;
}
function fomatFloat(src,pos){
return Math.round(src*Math.pow(10, pos))/Math.pow(10, pos);
}
//四舍五入
document.writeln("保留2位小数：" + toDecimal(3.14159267) + '<br/>');
document.writeln("强制保留2位小数：" + toDecimal2(3.14159267) + '<br/>');
document.writeln("保留2位小数：" + toDecimal(3.14559267) + '<br/>');
document.writeln("强制保留2位小数：" + toDecimal2(3.15159267) + '<br/>');
document.writeln("保留2位小数：" + fomatFloat(3.14559267, 2) + '<br/>');
document.writeln("保留1位小数：" + fomatFloat(3.15159267, 1) + '<br/>');
//五舍六入
document.writeln("保留2位小数：" + 1000.003.toFixed(2) + '<br/>');
document.writeln("保留1位小数：" + 1000.08.toFixed(1) + '<br/>');
document.writeln("保留1位小数：" + 1000.04.toFixed(1) + '<br/>');
document.writeln("保留1位小数：" + 1000.05.toFixed(1) + '<br/>');
//科学计数
document.writeln(3.1415.toExponential(2) + '<br/>');
document.writeln(3.1455.toExponential(2) + '<br/>');
document.writeln(3.1445.toExponential(2) + '<br/>');
document.writeln(3.1465.toExponential(2) + '<br/>');
document.writeln(3.1665.toExponential(1) + '<br/>');
//精确到n位，不含n位
document.writeln("精确到小数点第2位" + 3.1415.toPrecision(2) + '<br/>');
document.writeln("精确到小数点第3位" + 3.1465.toPrecision(3) + '<br/>');
document.writeln("精确到小数点第2位" + 3.1415.toPrecision(2) + '<br/>');
document.writeln("精确到小数点第2位" + 3.1455.toPrecision(2) + '<br/>');
document.writeln("精确到小数点第5位" + 3.141592679287.toPrecision(5) + '<br/>');
</script>
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<body>
This is my HTML page. <br>
</body>
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