{"id":4069,"date":"2024-07-15T18:01:13","date_gmt":"2024-07-15T11:01:13","guid":{"rendered":"https:\/\/www.marketenterprise.vn\/blog\/?p=4069"},"modified":"2024-07-23T10:26:58","modified_gmt":"2024-07-23T03:26:58","slug":"boundaries-and-anchors","status":"publish","type":"post","link":"https:\/\/www.marketenterprise.vn\/blog\/boundaries-and-anchors.html","title":{"rendered":"Kh\u00e1m ph\u00e1 v\u00e0i \u0111i\u1ec1u v\u1ec1 Boundaries v\u00e0 Anchors b\u1ea1n \u0111\u00e3 bi\u1ebft ch\u01b0a?"},"content":{"rendered":"

Ch\u00fang ta \u0111\u00e3 \u0111\u1ec1 c\u1eadp v\u1ec1 c\u00e1c k\u00fd t\u1ef1 \u0111\u1eb7c bi\u1ec7t (Special Characters<\/a>) trong b\u00e0i vi\u1ebft tr\u01b0\u1edbc, nh\u01b0ng ch\u01b0a \u0111i v\u00e0o chi ti\u1ebft v\u1ec1 ch\u1ee9c n\u0103ng v\u00e0 vai tr\u00f2 c\u1ee7a ch\u00fang. Trong b\u00e0i n\u00e0y, ch\u00fang ta s\u1ebd t\u1eadp trung v\u00e0o m\u1ed9t s\u1ed1 k\u00fd t\u1ef1 \u0111\u1eb7c bi\u1ec7t quan tr\u1ecdng nh\u01b0 ^, $, v\u00e0 \\. Nh\u1eefng k\u00fd t\u1ef1 n\u00e0y \u0111\u00f3ng vai tr\u00f2 quan tr\u1ecdng trong vi\u1ec7c x\u00e1c \u0111\u1ecbnh c\u00e1c v\u1ecb tr\u00ed ch\u00ednh x\u00e1c trong chu\u1ed7i m\u00e0 ch\u00fang ta c\u1ea7n ki\u1ec3m tra ho\u1eb7c x\u1eed l\u00fd. Th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ebft \u0111\u1ebfn d\u01b0\u1edbi hai t\u00ean g\u1ecdi ch\u00ednh l\u00e0 Boundaries (ranh gi\u1edbi) v\u00e0 Anchors (m\u1ecf neo).<\/p>\n

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Boundaries (ranh gi\u1edbi) v\u00e0 Anchors (m\u1ecf neo) l\u00e0 g\u00ec? Ch\u00fang l\u00e0m \u0111\u01b0\u1ee3c nh\u1eefng g\u00ec? C\u00f9ng kh\u00e1m ph\u00e1 l\u1ee3i \u00edch c\u1ee7a Anchors V\u00e0 Boundaries trong Regex.<\/span><\/p>\n

Anchors (M\u1ecf neo)<\/strong><\/h2>\n

\"Anchors(m\u1ecf<\/p>\n

Khi nh\u1eafc \u0111\u1ebfn Anchors<\/strong> trong Regex, l\u00e0 nh\u1eafc \u0111\u1ebfn ^ (Caret) v\u00e0 $ (Dollar sign).<\/span><\/p>\n

^ (Caret)<\/strong>: \u0110\u1eb7t \u1edf \u0111\u1ea7u m\u1ed9t bi\u1ec3u th\u1ee9c regex, ^<\/strong> bi\u1ec3u th\u1ecb r\u1eb1ng m\u1eabu c\u1ea7n kh\u1edbp ph\u1ea3i xu\u1ea5t hi\u1ec7n \u1edf \u0111\u1ea7u chu\u1ed7i. <\/span>V\u00ed d\u1ee5: bi\u1ec3u th\u1ee9c regex \/^Hello\/ <\/span>s\u1ebd kh\u1edbp v\u1edbi chu\u1ed7i “Hello world”<\/span> v\u00ec “Hello”<\/span> xu\u1ea5t hi\u1ec7n \u1edf \u0111\u1ea7u chu\u1ed7i. Nh\u01b0ng kh\u00f4ng kh\u1edbp v\u1edbi “I say: Hello”<\/span>, v\u00ec “I say: Hello”<\/span> kh\u00f4ng b\u1eaft \u0111\u1ea7u b\u1eb1ng “Hello”<\/span>.<\/span><\/p>\n

$ (Dollar sign)<\/strong>: \u0110\u1eb7t \u1edf cu\u1ed1i m\u1ed9t bi\u1ec3u th\u1ee9c regex, $<\/strong> bi\u1ec3u th\u1ecb r\u1eb1ng m\u1eabu c\u1ea7n kh\u1edbp ph\u1ea3i xu\u1ea5t hi\u1ec7n \u1edf cu\u1ed1i chu\u1ed7i (ho\u1eb7c cu\u1ed1i 1 d\u00f2ng<\/strong>). V\u00ed d\u1ee5: Bi\u1ec3u th\u1ee9c regex \/cat$\/<\/span> s\u1ebd kh\u1edbp v\u1edbi chu\u1ed7i “the white cat”<\/span> v\u00ec “cat”<\/span> xu\u1ea5t hi\u1ec7n \u1edf cu\u1ed1i chu\u1ed7i. C\u0169ng nh\u01b0 v\u1edbi ^ (Caret)<\/strong><\/span>, “The cat eats fish”<\/span> c\u00f3 k\u1ebft qu\u1ea3 kh\u00f4ng kh\u1edbp.<\/span><\/p>\n

Nh\u01b0 hai ph\u1ea7n m\u00f4 t\u1ea3 tr\u00ean th\u00ec \u0111i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 v\u1edbi ^ (Caret) v\u00e0 $ (Dollar sign), n\u1ebfu ch\u00fang \u0111\u01b0\u1ee3c \u0111\u1eb7t \u1edf v\u1ecb tr\u00ed kh\u00e1c m\u00e0 kh\u00f4ng \u0111\u00fang v\u1edbi v\u1ecb tr\u00ed nh\u01b0 trong m\u00f4 t\u1ea3 th\u00ec m\u1eabu s\u1ebd kh\u00f4ng kh\u1edbp v\u1edbi b\u1eaft k\u1ef3 chu\u1ed7i n\u00e0o.<\/span><\/em><\/p>\n

S\u1eed d\u1ee5ng k\u1ebft h\u1ee3p c\u1ea3 hai.<\/span><\/h4>\n

Tr\u01b0\u1eddng h\u1ee3p 1: Bi\u1ec3u th\u1ee9c regex (s\u1eed d\u1ee5ng c\u1ea3 hai Anchors) \/^\\d{3,10}$\/<\/span> kh\u1edbp v\u1edbi c\u00e1c chu\u1ed7i c\u00f3 t\u1eeb 3 \u0111\u1ebfn 10 ch\u1eef s\u1ed1.<\/span><\/p>\n