JavaScript 数字格式化函数

以下是4个有用的JS数字格式化函数  
1. 四舍五入 
下面两个函数都能对浮点数进行四舍五入，保留小数点后两位。 

2. 给数字添加逗号 
每三位数字添加一个逗号，方便阅读 

3. 类似PHP的 number_format 功能 
这个函数可以添加分隔逗号或者进行四舍五入。 

4. 添加序数词 
给数字添加"st, nd, rd, th"等序数词。 

1.四舍五入 

/** 下面两个函数都能对浮点数进行四舍五入，保留小数点后两位 **/ function CurrencyFormatted(amount) {    var i = parseFloat(amount);    if(isNaN(i)) { i = 0.00; }    var minus = '';    if(i < 0) { minus = '-'; }    i = Math.abs(i);    i = parseInt((i + .005) * 100);    i = i / 100;    s = new String(i);    if(s.indexOf('.') < 0) { s += '.00'; }    if(s.indexOf('.') == (s.length - 2)) { s += '0'; }    s = minus + s;    return s;}  /***   Usage:  CurrencyFormatted(12345.678);*   result: 12345.68**/ function format_number(pnumber,decimals){    if (isNaN(pnumber)) { return 0};    if (pnumber=='') { return 0};          var snum = new String(pnumber);    var sec = snum.split('.');    var whole = parseFloat(sec[0]);    var result = '';          if(sec.length > 1){        var dec = new String(sec[1]);        dec = String(parseFloat(sec[1])/Math.pow(10,(dec.length - decimals)));        dec = String(whole + Math.round(parseFloat(dec))/Math.pow(10,decimals));        var dot = dec.indexOf('.');        if(dot == -1){            dec += '.';            dot = dec.indexOf('.');        }        while(dec.length <= dot + decimals) { dec += '0'; }        result = dec;    } else{        var dot;        var dec = new String(whole);        dec += '.';        dot = dec.indexOf('.');            while(dec.length <= dot + decimals) { dec += '0'; }        result = dec;    }      return result;}  /***   Usage:  format_number(12345.678, 2);*   result: 12345.68**/

2.给数字添加逗号 

/** 每三位数字添加一个逗号，方便阅读 **/ function CommaFormatted(amount) {    var delimiter = ","; // replace comma if desired    amount = new String(amount);    var a = amount.split('.',2)    var d = a[1];    var i = parseInt(a[0]);    if(isNaN(i)) { return ''; }    var minus = '';    if(i < 0) { minus = '-'; }    i = Math.abs(i);    var n = new String(i);    var a = [];    while(n.length > 3)    {        var nn = n.substr(n.length-3);        a.unshift(nn);        n = n.substr(0,n.length-3);    }    if(n.length > 0) { a.unshift(n); }    n = a.join(delimiter);    if(d.length < 1) { amount = n; }    else { amount = n + '.' + d; }    amount = minus + amount;    return amount;}  /***   Usage:  CommaFormatted(12345678);*   result: 12,345,678**/ function addCommas(nStr) {    nStr += '';    var x = nStr.split('.');    var x1 = x[0];    var x2 = x.length >; 1 ? '.' + x[1] : '';    var rgx = /(d+)(d{3})/;          while (rgx.test(x1)) {        x1 = x1.replace(rgx, '$1' + ',' + '$2');    }          return x1 + x2;}  /***   Usage:  addCommas(12345678);*   result: 12,345,678**/

3.类似PHP的 number_format 功能

/** 这个函数可以添加分隔逗号或者进行四舍五入。 **/ function number_format (number, decimals, dec_point, thousands_sep) {      number = (number + '').replace(/[^0-9+-Ee.]/g, '');    var n = !isFinite(+number) ? 0 : +number,        prec = !isFinite(+decimals) ? 0 : Math.abs(decimals),        sep = (typeof thousands_sep === 'undefined') ? ',' : thousands_sep,        dec = (typeof dec_point === 'undefined') ? '.' : dec_point,        s = '',        toFixedFix = function (n, prec) {            var k = Math.pow(10, prec);            return '' + Math.round(n * k) / k;        };    // Fix for IE parseFloat(0.55).toFixed(0) = 0;    s = (prec ? toFixedFix(n, prec) : '' + Math.round(n)).split('.');    if (s[0].length > 3) {        s[0] = s[0].replace(/B(?=(?:d{3})+(?!d))/g, sep);    }    if ((s[1] || '').length < prec) {        s[1] = s[1] || '';        s[1] += new Array(prec - s[1].length + 1).join('0');    }    return s.join(dec);}  /***   Usage:  number_format(123456.789, 2, '.', ',');*   result: 123,456.79**/

4.添加序数词 

/** 给数字添加"st, nd, rd, th"等序数词。 **/ Number.prototype.toOrdinal = function() {    var n = this % 100;    var suffix = ['th', 'st', 'nd', 'rd', 'th'];    var ord = n < 21 ? (n < 4 ? suffix[n] : suffix[0]) : (n % 10 > 4 ? suffix[0] : suffix[n % 10]);    return this + ord;}  /**   Usage:*   var myNumOld = 23*   var myNumNew = myNumOld.toOrdinal()*   Result: 23rd*/

转自：http://www.oschina.net/code/snippet_28_7073