上网查询了一下 没有简单的方法所以自己经过1个小时的努力写出来了 郁闷

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function _format(pattern,num,z){
	var j =	pattern.length >= num.length ? pattern.length : num.length ;
	var p = pattern.split("");
	var n = num.split("");
	var bool = true,nn = "";
	for(var i=0;i<j;i++){
		var x = n[n.length-j+i];
		var y = p[p.length-j+i];
		if( z == 0){
			if(bool){
				if( ( x && y && (x != "0" || y == "0")) || ( x && x != "0" && !y ) || ( y && y == "0" && !x )  ){
					nn += x ? x : "0";
					bool = false;
				}	
			} else {
				nn +=  x ? x : "0" ;
			}
		} else {
			if( y && ( y == "0" || ( y == "#" && x ) ))
				nn += x ? x : "0" ;								
		}
	}
	return nn;
}
function _formatNumber(numChar,pattern){
	var patterns = pattern.split(".");
	var	numChars = numChar.split(".");
	var z = patterns[0].indexOf(",") == -1 ? -1 : patterns[0].length - patterns[0].indexOf(",") ;
	var num1 = _format(patterns[0].replace(","),numChars[0],0);
	var num2 = _format(	patterns[1]?patterns[1].split('').reverse().join(''):"", numChars[1]?numChars[1].split('').reverse().join(''):"",1);
	num1 =	num1.split("").reverse().join('');
	var reCat = eval("/[0-9]{" + (z-1) + "," + (z-1) + "}/gi");
	var arrdata = z > -1 ? num1.match(reCat) : undefined ;
	if( arrdata && arrdata.length > 0 ){
		var w =	num1.replace(arrdata.join(''),'');
		num1 = arrdata.join(',') + ( w == "" ? "" : "," ) + w ;
	}
	num1 = num1.split("").reverse().join("");
	return (num1 == "" ? "0" : num1) + (num2 != "" ? "." + num2.split("").reverse().join('') : "" ); 					
} 
function formatNumber(num,opt){
	var reCat = /[0#,.]{1,}/gi;
	var zeroExc = opt.zeroExc == undefined ? true : opt.zeroExc ;
	var pattern = opt.pattern.match(reCat)[0];
	var numChar = num.toString();
	return !(zeroExc && numChar == 0) ? opt.pattern.replace(pattern,_formatNumber(numChar,pattern)) : opt.pattern.replace(pattern,"0");
}

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下边是测试

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var n = 1234567890000;
    var p = "######.00";
    var x = formatNumber(n,{pattern:p});
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.01;
    var p = "#";
    var x = formatNumber(n,{pattern:p});
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    n = 1234567890000;
    p = "######.##";
    x = formatNumber(n,{pattern:p});
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");


    var n = 1234567890000.00;
    p = "######.##";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.00;
    p = "######.00";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.01;
    p = "######.00";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.01;
    p = "######.##";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.00;
    p = "###,###.##";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.01;
    p = "###,###.##";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.00;
    p = "##,####.##";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.01;
    p = "$###,###.##";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    var n = 1234567890000.01;
    p = "###,###.##元";
    x = formatNumber(n,{pattern:p})
    alert("n = " + n + "\n" + "p = " + p + "\n" + "x = " + x + "\n");

    va