c# - 用于匹配日期的正则表达式(月日、年或 m/d/yy)

Question

我正在尝试编写一个正则表达式，该表达式可用于在可能前面(或后面)有空格、数字、文本、行尾等的字符串中查找日期。该表达式应该处理 US日期格式是

1) 月名日、年 - 即 2019 年 1 月 10 日或
2) mm/dd/yy - 即 11/30/19

我找到了月份名称，日期年份

(Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4}

(在此感谢 Veverke Regex to match date like month name day comma and year

这对于 mm/dd/yy(以及 m/d/y 的各种组合)

(1[0-2]|0?[1-9])/(3[01]|[12][0-9]|0?[1-9])/(?:[0-9]{2})?[0-9]{2} 

(在此感谢 Steven Levithan 和 Jan Goyvaerts https://www.oreilly.com/library/view/regular-expressions-cookbook/9781449327453/ch04s04.html

我试过这样组合它们

((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4})|((1[0-2]|0?[1-9])/(3[01]|[12][0-9]|0?[1-9])/(?:[0-9]{2})?[0-9]{2})

当我在输入字符串“Paid on 1/1/2019”中搜索“on [regex above]”时，它确实找到了日期，但没有找到单词“on”。如果我只使用

就会找到该字符串

(1[0-2]|0?[1-9])/(3[01]|[12][0-9]|0?[1-9])/(?:[0-9]{2})?[0-9]{2}

谁能看出我做错了什么？

编辑

我正在使用下面的 c# .net 代码:

    string stringToSearch = "Paid on 1/1/2019";
    string searchPattern = @"on ((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4})|((1[0-2]|0?[1-9])/(3[01]|[12][0-9]|0?[1-9])/(?:[0-9]{2})?[0-9]{2})";
    var match = Regex.Match(stringToSearch, searchPattern, RegexOptions.IgnoreCase);


    string foundString;
    if (match.Success)
        foundString= stringToSearch.Substring(match.Index, match.Length);

例如

string searchPattern = @"on ((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4})|((1[0-2]|0?[1-9])/(3[01]|[12][0-9]|0?[1-9])/(?:[0-9]{2})?[0-9]{2})";
stringToSearch = "Paid on Jan 1, 2019";
found = "on Jan 1, 2019" -- worked as expected, found the word "on" and the date

stringToSearch = "Paid on 1/1/2019";
found = "1/1/2019"  -- did not work as expected, found the date but did not include the word "on"

如果我反转模式

string searchPattern = @"on ((1[0-2]|0?[1-9])/(3[01]|[12][0-9]|0?[1-9])/(?:[0-9]{2})?[0-9]{2})|((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4})"";

stringToSearch = "Paid on Jan 1, 2019";
found = "Jan 1, 2019" -- did not work as expected, found the date but did not include the word "on"

stringToSearch = "Paid on 1/1/2019";
found = "on 1/1/2019" -- worked as expected, found the word "on" and the date

谢谢

Answer 1

你的表达似乎很好，他们两个。如果您希望在目标输出之前或之后捕获任何内容，您只需在左右添加两个边界即可，这将为您完成。例如，请看this test :

(.*)(((1[0-2]|0?[1-9])\/(3[01]|[12][0-9]|0?[1-9])\/(?:[0-9]{2})?[0-9]{2})|((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4}))(.*)

例如，您可以在其中添加类似于 (.*) 的两个组，并将您的原始表达式包装在一个组中，这样就可以了。

正则表达式描述图

图表可视化您的表达式如何工作，您可能想测试此 link 中的其他表达式:

C# 测试

using System;
using System.Text.RegularExpressions;

public class Example
{
    public static void Main()
    {
        string pattern = @"(.*)(((1[0-2]|0?[1-9])\/(3[01]|[12][0-9]|0?[1-9])\/(?:[0-9]{2})?[0-9]{2})|((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4}))(.*)";
        string input = @"Paid on Jan 1, 2019 And anything else that you wish to have after
Paid on 1/1/2019 And anything else that you wish to have after";
        RegexOptions options = RegexOptions.Multiline;

        foreach (Match m in Regex.Matches(input, pattern, options))
        {
            Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
        }
    }
}

JavaScript 演示

此 JavaScript 演示表明您的表达式有效:

const regex = /(.*)(((1[0-2]|0?[1-9])\/(3[01]|[12][0-9]|0?[1-9])\/(?:[0-9]{2})?[0-9]{2})|((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4}))(.*)/gm;
const str = `Paid on Jan 1, 2019 And anything else that you wish to have after
Paid on 1/1/2019 And anything else that you wish to have after`;
const subst = `\nGroup 1: $1 \nGroup 2: $2 \nGroup 3: $3 \nGroup 4: $4 `;

// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);

console.log('Substitution result: ', result);

基本性能测试

此 JavaScript 片段返回 100 万次 for 循环的运行时间以提高性能。

const repeat = 1000000;
const start = Date.now();

for (var i = repeat; i >= 0; i--) {
	const string = 'Paid on Jan 1, 2019';
	const regex = /(.*)(((1[0-2]|0?[1-9])\/(3[01]|[12][0-9]|0?[1-9])\/(?:[0-9]{2})?[0-9]{2})|((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)\s+\d{1,2},\s+\d{4}))(.*)/gm;
	var match = string.replace(regex, "\nGroup #1: $1\nGroup #2: $2 \n");
}

const end = Date.now() - start;
console.log("YAAAY! \"" + match + "\" is a match 💚💚💚 ");
console.log(end / 1000 + " is the runtime of " + repeat + " times benchmark test. 😳 ");

改进

您可能希望减少围绕月份名称的捕获组，如果您愿意，您可以简单地将所有这些添加到一个捕获组中。