javascript 数字格式化

// Formats a number with grouped thousands    
// *     example 1: number_format(1234.56);  
// *     returns 1: '1,235'  
// *     example 2: number_format(1234.56, 2, ',', ' ');  
// *     returns 2: '1 234,56'  
// *     example 3: number_format(1234.5678, 2, '.', '');  
// *     returns 3: '1234.57'  
// *     example 4: number_format(67, 2, ',', '.');      
// *     returns 4: '67,00'  
// *     example 5: number_format(1000);  
// *     returns 5: '1,000'  
// *     example 6: number_format(67.311, 2);  
// *     returns 6: '67.31'  
// *     example 7: number_format(1000.55, 1);  
// *     returns 7: '1,000.6'  
// *     example 8: number_format(67000, 5, ',', '.');  
// *     returns 8: '67.000,00000'  
// *     example 9: number_format(0.9, 0);      
// *     returns 9: '1'  
// *     example 10: number_format('1.20', 2);  
// *     returns 10: '1.20'  
// *     example 11: number_format('1.20', 4);  
// *     returns 11: '1.2000'      
// *     example 12: number_format('1.2000', 3);  
// *     returns 12: '1.200'  
/** 
 * number_format 
 * 
 * @param int or float number 
 * @param int          decimals 
 * @param string       dec_point 
 * @param string       thousands_sep 
 * @return string 
 */  
function number_format(number, decimals, dec_point, thousands_sep) {  
    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);  
}