js数字格式化(截断格式化或四舍五入格式化)

/***
 * 数字格式化(适合金融产品截断小数位后展示)
 * @param num
 * @param pattern (标准格式：#,###.## 或#.## 或#,###00.00)
 * @param round 1=四舍五入后格式化；0=截断格式化
 * @returns {string}
 */
function formatNumber(num, pattern, round) {
    if (num && !/^[\d\.]+$/g.test(num)) {
        console.log("the number format is incorrect！");
        return "";
    }

    var formatLeft = "";
    var formatRight = "";
    var symbolFlag = pattern.lastIndexOf(".");
    if (symbolFlag == -1) {
        formatLeft = pattern;
    } else {
        formatLeft = pattern.substring(0, pattern.lastIndexOf("."));
        formatRight = pattern.substring(pattern.lastIndexOf(".") + 1, pattern.length);
    }
    //四舍五入
    if (round == 1) {
        num = new Number(num).toFixed(formatRight.length);
    }

    //格式化数字
    var numberLeft = "";
    var numberRight = "";
    var numSymbolFlag = num.lastIndexOf(".");
    if (numSymbolFlag == -1) {
        var numberLeft = num;
    } else {
        var numberLeft = num.substring(0, num.lastIndexOf("."));
        var numberRight = num.substring(num.lastIndexOf(".") + 1, num.length);
    }

    var numberBucket = new Array();
    var formatFlag = formatLeft.indexOf("#,###");//千位符标记
    var count = 1;
    var len = numberLeft.length;
    for (var i = len; i > 0; i--) {
        numberBucket.unshift(numberLeft.charAt(i - 1));
        if (formatFlag != -1) {
            if (count % 3 == 0 && count != len) {
                numberBucket.unshift(',');
            }
        }
        count++;
    }
    if (symbolFlag != -1) {
        numberBucket.push('.');
    }
    for (var i = 0; i < formatRight.length; i++) {
        if (formatRight.charAt(i) && numberRight.charAt(i)) {
            numberBucket.push(numberRight.charAt(i))
        } else {
            numberBucket.push("0");
        }
    }
    return numberBucket.join("");
}

//测试
document.writeln(formatNumber("123456789.123456", "#") + "<br/>");
document.writeln(formatNumber("123456789.123456", "#.#")+ "<br/>");
document.writeln(formatNumber("123456789.123456", "#,###") + "<br/>");
document.writeln(formatNumber("123456789.123456", "#,###.#")+ "<br/>");
document.writeln(formatNumber("123456789.123456", "#,###.#")+ "<br/>");document.writeln(formatNumber("123456789.123456", "#,###.####")+ "<br/>");document.writeln(formatNumber("1.50", "#.#", 1) + "<br/>");document.writeln(formatNumber("1.125456", "#.#", 1) + "<br/>");document.writeln(formatNumber("1.125456", "#.##", 1) + "<br/>");
document.writeln(formatNumber("1.125456", "#.###", 1) + "<br/>");
document.writeln(formatNumber("1.125456", "#.####", 1) + "<br/>");
document.writeln(formatNumber("1.125456", "#.#####", 1) + "<br/>");