正则表达式用逗号分隔数千并保留两位小数

问题描述：

我最近在回答另一个*问题时想出了这段代码。基本上，在模糊时，这段代码将正确地用逗号分隔数千，并将小数保留为两位数（如美元的写法[7,745.56]）。

I recently came up with this code while answering another * question. Basically, on blur, this code will properly comma separate by thousands and leave the decimal at two digits (like how USD is written [7,745.56]).

我想知道是否有更简洁的方法使用正则表达式来分隔和切断过多的小数位。我最近用最近的尝试更新了这篇文章。使用正则表达式有更好的方法吗？

I was wondering if there is more concise way of using regex to , separate and cut off excessive decimal places. I recently updated this post with my most recent attempt. Is there a better way of doing this with regex?

7456 -> 7,456
45345 -> 45,345
25.23523534 -> 25.23
3333.239 -> 3,333.23
234.99 -> 234.99
2300.99 -> 2,300.99
23123123123.22 -> 23,123,123,123.22

当前正则表达式

Current Regex

var result;
var str = []
reg = new RegExp(/(\d*(\d{2}\.)|\d{1,3})/, "gi");
reversed = "9515321312.2323432".split("").reverse().join("")
while (result = reg.exec(reversed)) {
  str.push(result[2] ? result[2] : result[0])
}
console.log(str.join(",").split("").reverse().join("").replace(",.","."))

答

如果你真的坚持纯正在使用正则表达式（并截断而不是舍入小数位），我能想到的唯一解决方案是使用替换函数作为的第二个参数.replace（）：

If you really insist on doing this purely in regex (and truncate instead of round the fractional digits), the only solution I can think of is to use a replacement function as the second argument to .replace():

('' + num).replace(
  /(\d)(?=(?:\d{3})+(?:\.|$))|(\.\d\d?)\d*$/g, 
  function(m, s1, s2){
    return s2 || (s1 + ',');
  }
);

这使您的所有测试用例都通过：

This makes all your test cases pass:

function format(num){
  return ('' + num).replace(
    /(\d)(?=(?:\d{3})+(?:\.|$))|(\.\d\d?)\d*$/g, 
    function(m, s1, s2){
      return s2 || (s1 + ',');
    }
  );
}


test(7456, "7,456");
test(45345, "45,345");
test(25.23523534, "25.23"); //truncated, not rounded
test(3333.239, "3,333.23"); //truncated, not rounded
test(234.99, "234.99");
test(2300.99, "2,300.99");
test(23123123123.22, "23,123,123,123.22");

function test(num, expected){
  var actual = format(num);
  console.log(num + ' -> ' + expected + ' => ' + actual + ': ' + 
    (actual === expected ? 'passed' : 'failed')
   );
}

正则表达式用逗号分隔数千并保留两位小数

当前正则表达式

Current Regex

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