数值千分位，6种方法和性能对比，值得一看

function format_with_array(number) {
    var arr = (number + '').split('.');
    var int = arr[0].split('');
    var fraction = arr[1] || '';
    var r = "";
    var len = int.length;
    int.reverse().forEach(function (v, i) {
        if (i !== 0 && i % 3 === 0) {
            r = v + "," + r;
        } else {
            r = v + r;
        }
    })
    return r + (!!fraction ? "." + fraction : '');
}
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function format_with_substring(number) {
    var arr = (number + '').split('.');
    var int = arr[0] + '';
    var fraction = arr[1] || '';
    var f = int.length % 3;
    var r = int.substring(0, f);
    for (var i = 0; i < Math.floor(int.length / 3); i++) {
        r += ',' + int.substring(f + i * 3, f + (i + 1) * 3)
    }
    if (f === 0) {
        r = r.substring(1);
    }
    return r + (!!fraction ? "." + fraction : '');
}
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function format_with_mod(number) {
    var n = number;
    var r = ""; 
    var temp;
    do {
        mod = n % 1000;
        n = n / 1000;
        temp = ~~mod;
        r =  (n >= 1 ?`${temp}`.padStart(3, "0"): temp) + (!!r ? "," + r : "")
    } while (n >= 1)
    var strNumber = number + "";
    var index = strNumber.indexOf(".");
    if (index > 0) {
        r += strNumber.substring(index);
    }
    return r;
}
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function format_with_regex(number) {
    var reg = /\d{1,3}(?=(\d{3})+$)/g;
    return (number + '').replace(reg, '$&,');
}
function format_with_regex(number) {
    var reg = /(\d)(?=(?:\d{3})+$)/g   
    return (number + '').replace(reg, '$1,');
}
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function format_with_toLocaleString(number, minimumFractionDigits, maximumFractionDigits) {
    minimumFractionDigits = minimumFractionDigits || 2;
    maximumFractionDigits = (maximumFractionDigits || 2);
    maximumFractionDigits = Math.max(minimumFractionDigits, maximumFractionDigits);
    return number.toLocaleString("en-us", {
        maximumFractionDigits: maximumFractionDigits || 2,
        minimumFractionDigits: minimumFractionDigits || 2
    })
}
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function format_with_Intl(number, minimumFractionDigits, maximumFractionDigits) {
    minimumFractionDigits = minimumFractionDigits || 2;
    maximumFractionDigits = (maximumFractionDigits || 2);
    maximumFractionDigits = Math.max(minimumFractionDigits, maximumFractionDigits);
    return new Intl.NumberFormat('en-us', {
        maximumFractionDigits: maximumFractionDigits || 2,
        minimumFractionDigits: minimumFractionDigits || 2
    }).format(number)
}
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function getData(count) {
    var data = new Array(count).fill(0).map(function (i) {
        var rd = Math.random();
        var r = rd * Math.pow(10, 10);
        if (rd > 0.5) {
            r = ~~r;
        }
        return r
    })
    return data;
}
function test(data, fn, label) {
    var start = performance.now();
    for (var i = 0; i < data.length; i++) {
        fn(data[i]);
    }
    var time = performance.now() - start;
    message((fn.name || label) + ":" + time + "ms");
}
function executeTest() {
    var data = getData(+textCount.value);
    test(data, format_with_array);
    test(data, format_with_mod);
    test(data, format_with_substring);
    test(data, format_with_regex);
    test(data, format_with_toLocaleString);
    test(data, format_with_Intl);
}
function message(msg) {
    var el = document.createElement("p");
    el.innerHTML = msg;
    messageEl.appendChild(el);
}
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