JavaScript 实现数字千分位格式化（每三位加逗号）的六种方法

function toThousands(num) {
    var result = [ ], counter = 0;
    num = (num || 0).toString().split('');
    for (var i = num.length - 1; i >= 0; i--) {
        counter++;
        result.unshift(num[i]);
        if (!(counter % 3) && i != 0) { result.unshift(','); }
    }
    return result.join('');
}

function toThousands(num) {
    var result = '', counter = 0;
    num = (num || 0).toString();
    for (var i = num.length - 1; i >= 0; i--) {
        counter++;
        result = num.charAt(i) + result;
        if (!(counter % 3) && i != 0) { result = ',' + result; }
    }
    return result;
}

function toThousands(num) {
    var num = (num || 0).toString(), re = /\d{3}$/, result = '';
    while ( re.test(num) ) {
        result = RegExp.lastMatch + result;
        if (num !== RegExp.lastMatch) {
            result = ',' + result;
            num = RegExp.leftContext;
        }
        else {
            num = '';
            break;
        }
    }
    if (num) { result = num + result; }
    return result;
}

function toThousands(num) {
    var num = (num || 0).toString(), result = '';
    while (num.length > 3) {
        result = ',' + num.slice(-3) + result;
        num = num.slice(0, num.length - 3);
    }
    if (num) { result = num + result; }
    return result;
}

function toThousands(num) {
    var num = (num || 0).toString(), temp = num.length % 3;
    switch (temp) {
        case 1:
        num = '00' + num;
        break;
        case 2:
        num = '0' + num;
        break;
    }
    return num.match(/\d{3}/g).join(',').replace(/^0+/, '');
}

function toThousands(num) {
    return (num || 0).toString().replace(/(\d)(?=(?:\d{3})+$)/g, '$1,');
}