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本文介紹了如何在 JavaScript 中用逗號打印一個數字作為千位分隔符的處理方法，對大家解決問題具有一定的參考價值，需要的朋友們下面隨著小編來一起學習吧！

問題描述

限時送ChatGPT賬號..

我正在嘗試在 JavaScript 中打印一個整數，并用逗號作為千位分隔符.例如，我想將數字 1234567 顯示為1,234,567".我該怎么做呢?

I am trying to print an integer in JavaScript with commas as thousands separators. For example, I want to show the number 1234567 as "1,234,567". How would I go about doing this?

這是我的做法:

function numberWithCommas(x) {
    x = x.toString();
    var pattern = /(-?d+)(d{3})/;
    while (pattern.test(x))
        x = x.replace(pattern, "$1,$2");
    return x;
}

有沒有更簡單或更優雅的方法來做到這一點?如果它也適用于浮點數會很好，但這不是必需的.在句點和逗號之間決定不需要特定于語言環境.

Is there a simpler or more elegant way to do it? It would be nice if it works with floats also, but that is not necessary. It does not need to be locale-specific to decide between periods and commas.

推薦答案

我使用了 Kerry 的回答中的想法，但簡化了它，因為我只是為我的特定目的尋找簡單的東西.這是我所擁有的:

I used the idea from Kerry's answer, but simplified it since I was just looking for something simple for my specific purpose. Here is what I have:

function numberWithCommas(x) {
    return x.toString().replace(/B(?=(d{3})+(?!d))/g, ",");
}

function numberWithCommas(x) {
    return x.toString().replace(/B(?<!.d*)(?=(d{3})+(?!d))/g, ",");
}

function test(x, expect) {
    const result = numberWithCommas(x);
    const pass = result === expect;
    console.log(`${pass ? "?" : "ERROR ====>"} ${x} => ${result}`);
    return pass;
}

let failures = 0;
failures += !test(0,        "0");
failures += !test(100,      "100");
failures += !test(1000,     "1,000");
failures += !test(10000,    "10,000");
failures += !test(100000,   "100,000");
failures += !test(1000000,  "1,000,000");
failures += !test(10000000, "10,000,000");
if (failures) {
    console.log(`${failures} test(s) failed`);
} else {
    console.log("All tests passed");
}

.as-console-wrapper {
    max-height: 100% !important;
}

正則表達式使用 2 個前瞻斷言:

The regex uses 2 lookahead assertions:

一個正數，用于查找字符串中后面連續有 3 個數字的倍數的任何點，
一個否定斷言，以確保該點僅具有 3 位數字的倍數.替換表達式在此處放置一個逗號.

例如，如果你傳遞它 123456789.01，肯定斷言將匹配 7 左邊的每個點(因為 789 是 3 位的倍數，678 是 3 位的倍數，567 等).否定斷言檢查 3 位的倍數后面沒有任何數字.789 后面有一個句點，所以它正好是 3 位數字的倍數，所以用逗號.678 是 3 位數字的倍數，但它后面有一個 9，所以這 3 位數字是一組 4 的一部分，逗號不會去那里.567 也是如此.456789 是 6 位數字，是 3 的倍數，所以前面要加逗號.345678 是 3 的倍數，但它后面有一個 9，所以那里沒有逗號.等等.B 防止正則表達式在字符串開頭放置逗號.

For example, if you pass it 123456789.01, the positive assertion will match every spot to the left of the 7 (since 789 is a multiple of 3 digits, 678 is a multiple of 3 digits, 567, etc.). The negative assertion checks that the multiple of 3 digits does not have any digits after it. 789 has a period after it so it is exactly a multiple of 3 digits, so a comma goes there. 678 is a multiple of 3 digits but it has a 9 after it, so those 3 digits are part of a group of 4, and a comma does not go there. Similarly for 567. 456789 is 6 digits, which is a multiple of 3, so a comma goes before that. 345678 is a multiple of 3, but it has a 9 after it, so no comma goes there. And so on. The B keeps the regex from putting a comma at the beginning of the string.

@neu-rah 提到如果后面有超過 3 個數字，這個函數會在不需要的地方添加逗號小數點.如果這是一個問題，你可以使用這個功能:

@neu-rah mentioned that this function adds commas in undesirable places if there are more than 3 digits after the decimal point. If this is a problem, you can use this function:

function numberWithCommas(x) {
    var parts = x.toString().split(".");
    parts[0] = parts[0].replace(/B(?=(d{3})+(?!d))/g, ",");
    return parts.join(".");
}

function numberWithCommas(x) {
    var parts = x.toString().split(".");
    parts[0] = parts[0].replace(/B(?=(d{3})+(?!d))/g, ",");
    return parts.join(".");
}

function test(x, expect) {
    const result = numberWithCommas(x);
    const pass = result === expect;
    console.log(`${pass ? "?" : "ERROR ====>"} ${x} => ${result}`);
    return pass;
}

let failures = 0;
failures += !test(0              , "0");
failures += !test(0.123456       , "0.123456");
failures += !test(100            , "100");
failures += !test(100.123456     , "100.123456");
failures += !test(1000           , "1,000");
failures += !test(1000.123456    , "1,000.123456");
failures += !test(10000          , "10,000");
failures += !test(10000.123456   , "10,000.123456");
failures += !test(100000         , "100,000");
failures += !test(100000.123456  , "100,000.123456");
failures += !test(1000000        , "1,000,000");
failures += !test(1000000.123456 , "1,000,000.123456");
failures += !test(10000000       , "10,000,000");
failures += !test(10000000.123456, "10,000,000.123456");
if (failures) {
    console.log(`${failures} test(s) failed`);
} else {
    console.log("All tests passed");
}

.as-console-wrapper {
    max-height: 100% !important;
}

@tjcrowder 指出，現在 JavaScript 有lookbehind (支持信息)，可以在正則表達式本身解決:

@t.j.crowder pointed out that now that JavaScript has lookbehind (support info), it can be solved in the regular expression itself:

function numberWithCommas(x) {
    return x.toString().replace(/B(?<!.d*)(?=(d{3})+(?!d))/g, ",");
}

function numberWithCommas(x) {
    return x.toString().replace(/B(?<!.d*)(?=(d{3})+(?!d))/g, ",");
}

function test(x, expect) {
    const result = numberWithCommas(x);
    const pass = result === expect;
    console.log(`${pass ? "?" : "ERROR ====>"} ${x} => ${result}`);
    return pass;
}

let failures = 0;
failures += !test(0,               "0");
failures += !test(0.123456,        "0.123456");
failures += !test(100,             "100");
failures += !test(100.123456,      "100.123456");
failures += !test(1000,            "1,000");
failures += !test(1000.123456,     "1,000.123456");
failures += !test(10000,           "10,000");
failures += !test(10000.123456,    "10,000.123456");
failures += !test(100000,          "100,000");
failures += !test(100000.123456,   "100,000.123456");
failures += !test(1000000,         "1,000,000");
failures += !test(1000000.123456,  "1,000,000.123456");
failures += !test(10000000,        "10,000,000");
failures += !test(10000000.123456, "10,000,000.123456");
if (failures) {
    console.log(`${failures} test(s) failed`);
} else {
    console.log("All tests passed");
}

.as-console-wrapper {
    max-height: 100% !important;
}

(?<!.d*) 是一個否定的lookbehind，表示匹配項前面不能有 . 后跟零個或多個數字.負面的lookbehind比split和join解決方案更快(比較)，至少在 V8 中.

(?<!.d*) is a negative lookbehind that says the match can't be preceded by a . followed by zero or more digits. The negative lookbehind is faster than the split and join solution (comparison), at least in V8.

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如何在 JavaScript 中用逗號打印一個數字作為千位

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