匹配此字符串的正則表達式是什么？

Question

考慮以下句子：

蘋果是2公斤
蘋果香蕉芒果是2公斤
蘋果蘋果蘋果6公斤
香蕉香蕉香蕉6kg

鑒於“蘋果”，“香蕉”和“芒果”是唯一的水果，提取出現在句子開頭的水果名稱的正則表達式是什么？

我寫了這個正則表達式（ https://regex101.com/r/fY8bK1/1 ）：

^(apple|mango|banana) is (\d+)kg$  

但這僅在句子中只有一個水果時才匹配。

如何提取所有水果名稱？

所有4個句子的預期輸出應為：

蘋果2
蘋果香蕉芒果2
蘋果蘋果蘋果6
香蕉香蕉香蕉6

Answer 1

您可以像這樣使用分組：

^((?:apple|mango|banana)(?:\s+(?:apple|mango|banana))*) is (\d+)kg$

見正則表達式演示

(?:...)是捕獲（ (...) ）組中的一個非捕獲組，以免在輸出中造成混亂。

((?:apple|mango|banana)(?:\\s+(?:apple|mango|banana))*)組匹配：

• (?:apple|mango|banana) -替代列表中以交替符分隔的任何值| 操作員。 如果您打算只匹配整個單詞，請在子模式的兩端放置\\b 。
• (?:\\s+(?:apple|mango|banana))*匹配0個或多個序列...
  • \\s+ -1個或多個空格
  • (?:apple|mango|banana) -任何其他選擇。

片段：

 var re = /^((?:apple|mango|banana)(?:\\s+(?:apple|mango|banana))*) is (\\d+)kg$/gm; var str = 'apple is 2kg\\napple banana mango is 2kg\\napple apple apple is 6kg\\nbanana banana banana is 6kg'; var m; while ((m = re.exec(str)) !== null) { document.write(m[1] + "," + m[2] + "<br/>"); } document.write("<b>appleapple is 2kg</b> matched: " + /^((?:apple|mango|banana)(?:\\s+(?:apple|mango|banana))*) is (\\d+)kg$/.test("appleapple is 2kg")); 

Answer 2

嘗試這個

var re = /^((?:(?:apple|banana|mango)(?= ) ?)+) is (\d+)kg$/gm;

re.exec('apple banana mango is 2kg');
// ["apple banana mango is 2kg", "apple banana mango", "2"]

這與其他答案有何不同？ (?= ) ? 在水果選項強制使用空格作為下一個字符之后，除非有更多的水果（否則您將is換成兩倍），否則不會捕獲它。

在while循環中使用它可以從多行字符串中獲取所有結果。

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此處的gm標志使用re.exec將此RegExp多次應用於同一String ，其中新行匹配$^ 。 但是， g標志導致str.match表現不同。

如果要對每個字符串進行獨立測試，則可以繼續使用re.exec或刪除這些標志並改用str.match

var re = /^((?:(?:apple|banana|mango)(?= ) ?)+) is (\d+)kg$/; // notice flags gone

'apple banana mango is 2kg'.match(re);
// ["apple banana mango is 2kg", "apple banana mango", "2"]

Answer 3

/^(((apple|mango|banana)\s*)+) is (\d+)kg$/$1,$4/gm

演示： https : //regex101.com/r/sA4aW7/2

因此，您從這里開始，其中之一：

(apple|mango|banana)

讓我們得到最終的空格分隔重復：

(apple|mango|banana)\s*

以及所有（至少一個）重復：

((apple|mango|banana)\s*)+

需要添加一個額外的組，因為您想要一個組來捕獲批次：

(((apple|mango|banana)\s*)+)

加上這一點， $1 （最外面的組）將包含“ banana banana banana ...”； 第四，你的體重。 添加您自己?:避免捕獲內群體，如果你喜歡 。

Answer 4

^((?:apple|mango|banana| )+) is (\d+)kg\s?$/gmi

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演示

https://regex101.com/r/dO1rR7/1

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說明

^((?:apple|mango|banana| )+) is (\d+)kg\s?$/gmi

^ assert position at start of a line
1st Capturing group ((?:apple|mango|banana| )+)
    (?:apple|mango|banana| )+ Non-capturing group
        Quantifier: + Between one and unlimited times, as many times as possible, giving back as needed [greedy]
        1st Alternative: apple
            apple matches the characters apple literally (case sensitive)
        2nd Alternative: mango
            mango matches the characters mango literally (case sensitive)
        3rd Alternative: banana
            banana matches the characters banana literally (case sensitive)
        4th Alternative:  
             matches the character  literally
 is matches the characters  is literally (case sensitive)
2nd Capturing group (\d+)
    \d+ match a digit [0-9]
        Quantifier: + Between one and unlimited times, as many times as possible, giving back as needed [greedy]
kg matches the characters kg literally (case sensitive)
\s? match any white space character [\r\n\t\f ]
    Quantifier: ? Between zero and one time, as many times as possible, giving back as needed [greedy]
$ assert position at end of a line
g modifier: global. All matches (don't return on first match)
m modifier: multi-line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])