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  • js除法四舍五入保留小数点后两位写法

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">   
    <html>    
    <head>  
    <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=UTF-8">   
    <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   
    alert("保留2位小数:" + toDecimal(3.14159267));  
    alert("强制保留2位小数:" + toDecimal2(3.14159267));
    alert("保留2位小数:" + toDecimal(3.14559267));   
    alert("强制保留2位小数:" + toDecimal2(3.15159267));   
    alert("保留2位小数:" + fomatFloat(3.14559267, 2));
    alert("保留1位小数:" + fomatFloat(3.15159267, 1));   
    //五舍六入    
    alert("保留2位小数:" + 1000.003.toFixed(2));          
    alert("保留1位小数:" + 1000.08.toFixed(1));   
    alert("保留1位小数:" + 1000.04.toFixed(1));     
    alert("保留1位小数:" + 1000.05.toFixed(1));    
    //科学计数  
    alert(3.1415.toExponential(2));      
    alert(3.1455.toExponential(2));   
    alert(3.1445.toExponential(2));  
    alert(3.1465.toExponential(2));  
    alert(3.1665.toExponential(1));   
    //精确到n位,不含n位      
    alert("精确到小数点第2位" + 3.1415.toPrecision(2));   
    alert("精确到小数点第3位" + 3.1465.toPrecision(3));  
    alert("精确到小数点第2位" + 3.1415.toPrecision(2));  
    alert("精确到小数点第2位" + 3.1455.toPrecision(2));    
    alert("精确到小数点第5位" + 3.141592679287.toPrecision(5));      
    </script>    
    </head>
    <body>
    This is my HTML page. <br>   
    </body> 
    </html>

    另外,toFixed();获得小数点后面多少位数字。五舍六入的方法。

    var floatNum = 5.234 

    var temp = floatNum.toFixed(1);    //相当于var temp = 5.2 

    Math.pow(x,y) -- 返回底数的指定次幂

    document.write(Math.pow(2,10));
    document.write(Math.pow(1024,0.1));
    document.write(Math.pow(2,0));
    document.write(Math.pow(99,9999));
    //结果:
    1024
    2
    1
    Infinity

    博客原文:http://www.cnblogs.com/alana/archive/2012/11/26/2788566.html

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  • 原文地址:https://www.cnblogs.com/shy1766IT/p/4477414.html
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