如何在JavaScript中使用逗号作为千位分隔符来打印数字 [英] How to print a number with commas as thousands separators in JavaScript

问题描述

我正在尝试在 JavaScript 中使用逗号作为千位分隔符来打印整数。例如，我想显示编号1234567为1,234,567。我怎么去做这个？

这是我如何做的：

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





$ b

有没有更简单或更优雅的方式来做到这一点？这将是很好，如果它也适用于浮动，但这不是必要的。它不需要特定于语言环境来决定句点和逗号。

解决方案

我使用了Kerry的答案，但简化了它，因为我只是为了特定目的寻找简单的东西。这是我做的：

  const numberWithCommas =（x）=> {
 return x.toString（）。replace（/ \B（？=（\d {3}）+（?! \d））/ g，，）; 
 
 
 
 $ b $ p 
 $ b 
这就是你真正需要知道的。
 
 
 @Neils Bom询问正则表达式是如何工作的。我的解释有点长。它不适合的评论，我不知道还有什么地方，所以我在这里做。如果有人有任何其他的建议，请告诉我。
 
 
 
正则表达式使用2个前瞻断言：正面的一个查找字符串中的任意点在它之后的一行中有3位数的倍数，并且有一个否定的断言来确保这个点只有3位数的整数倍。例如，如果你通过它123456789.01，肯定的断言将匹配7的左边的每一个点（因为/ 789是3位的倍数，678是3位的倍数，567等）。否定断言检查3位数的倍数之后没有任何数字。 789之后有一段时间，所以它恰好是3位数的倍数，所以逗号在那里。 678是3位数的倍数，但它后面有一个9，所以这3位数字是一组4的一部分，逗号不会去那里。类似的567。 456789是6位数字，是3的倍数，所以前面有一个逗号。 345678是3的倍数，但它之后有一个9，所以没有逗号。等等。 \B使得正则表达式不会在字符串的开头加一个逗号。
 
 
 
 @ neu-rah提到这个函数在不需要的地方添加了逗号小数点后3位以上。如果这是一个问题，你可以使用这个函数：
 
 
  const numberWithCommas =（x）=> {
 var parts = x.toString（）。split（。）; 
 parts [0] = parts [0] .replace（/ \B（？=（\d {3}）+（?! \ d））/ g，，）; 
 return parts.join（。）; 
} 
  
 
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? 

Here is how I am doing it:
function numberWithCommas(x) {
    x = x.toString();
    var pattern = /(-?\d+)(\d{3})/;
    while (pattern.test(x))
        x = x.replace(pattern, "$1,$2");
    return x;
}
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. 
解决方案
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 did:
const numberWithCommas = (x) => {
  return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
}
This is all you really need to know.

@Neils Bom asked how the regex works. My explanation is sort of long. It won't fit in the comments and I don't know where else to put it so I am doing it here. If anyone has any other suggestions for where to put it, please let me know.

The regex uses 2 lookahead assertions: a positive one to look for any point in the string that has a multiple of 3 digits in a row after it, and a negative assertion to make sure that point only has exactly a multiple of 3 digits. The replacement expression puts a comma there.

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


                        
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