From ee778d6eea54935fd05022e0ba8c49456003381a Mon Sep 17 00:00:00 2001 From: Florian Merz Date: Thu, 11 Feb 2021 14:48:24 +0100 Subject: unslug ko: move --- .../assertions/index.html" | 244 --------------------- 1 file changed, 244 deletions(-) delete mode 100644 "files/ko/web/javascript/guide/\354\240\225\352\267\234\354\213\235/assertions/index.html" (limited to 'files/ko/web/javascript/guide/정규식/assertions/index.html') diff --git "a/files/ko/web/javascript/guide/\354\240\225\352\267\234\354\213\235/assertions/index.html" "b/files/ko/web/javascript/guide/\354\240\225\352\267\234\354\213\235/assertions/index.html" deleted file mode 100644 index 350c50f8f9..0000000000 --- "a/files/ko/web/javascript/guide/\354\240\225\352\267\234\354\213\235/assertions/index.html" +++ /dev/null @@ -1,244 +0,0 @@ ---- -title: Assertions -slug: Web/JavaScript/Guide/정규식/Assertions -translation_of: Web/JavaScript/Guide/Regular_Expressions/Assertions ---- -

{{jsSidebar("JavaScript Guide")}}

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Assertions에는 행이나 단어의 시작 · 끝을 나타내는 경계와 (앞, 뒤 읽고 조건식을 포함한) 어떤 식 으로든 매치가 가능한 것을 나타내는 다른 패턴이 포함됩니다.

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{{EmbedInteractiveExample("pages/js/regexp-assertions.html", "taller")}}
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Types

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Boundary-type assertions

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CharactersMeaning
^ -

Matches the beginning of input. If the multiline flag is set to true, also matches immediately after a line break character. For example, /^A/ does not match the "A" in "an A", but does match the first "A" in "An A".

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This character has a different meaning when it appears at the start of a group.

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Matches the end of input. If the multiline flag is set to true, also matches immediately before a line break character. For example, /t$/ does not match the "t" in "eater", but does match it in "eat".

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\b -

Matches a word boundary. This is the position where a word character is not followed or preceded by another word-character, such as between a letter and a space. Note that a matched word boundary is not included in the match. In other words, the length of a matched word boundary is zero.

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Examples:

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  • /\bm/ matches the "m" in "moon".
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  • /oo\b/ does not match the "oo" in "moon", because "oo" is followed by "n" which is a word character.
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  • /oon\b/ matches the "oon" in "moon", because "oon" is the end of the string, thus not followed by a word character.
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  • /\w\b\w/ will never match anything, because a word character can never be followed by both a non-word and a word character.
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To match a backspace character ([\b]), see Character Classes.

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\B -

Matches a non-word boundary. This is a position where the previous and next character are of the same type: Either both must be words, or both must be non-words, for example between two letters or between two spaces. The beginning and end of a string are considered non-words. Same as the matched word boundary, the matched non-word boundary is also not included in the match. For example, /\Bon/ matches "on" in "at noon", and /ye\B/ matches "ye" in "possibly yesterday".

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Other assertions

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Note: The ? character may also be used as a quantifier.

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CharactersMeaning
x(?=y) -

Lookahead assertion: Matches "x" only if "x" is followed by "y". For example, /Jack(?=Sprat)/ matches "Jack" only if it is followed by "Sprat".
- /Jack(?=Sprat|Frost)/ matches "Jack" only if it is followed by "Sprat" or "Frost". However, neither "Sprat" nor "Frost" is part of the match results.

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x(?!y) -

Negative lookahead assertion: Matches "x" only if "x" is not followed by "y". For example, /\d+(?!\.)/ matches a number only if it is not followed by a decimal point. /\d+(?!\.)/.exec('3.141') matches "141" but not "3.

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Lookbehind assertion: Matches "x" only if "x" is preceded by "y". For example, /(?<=Jack)Sprat/ matches "Sprat" only if it is preceded by "Jack". /(?<=Jack|Tom)Sprat/ matches "Sprat" only if it is preceded by "Jack" or "Tom". However, neither "Jack" nor "Tom" is part of the match results.

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Negative lookbehind assertion: Matches "x" only if "x" is not preceded by "y". For example, /(?<!-)\d+/ matches a number only if it is not preceded by a minus sign. /(?<!-)\d+/.exec('3') matches "3". /(?<!-)\d+/.exec('-3')  match is not found because the number is preceded by the minus sign.

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Examples

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General boundary-type overview example

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// Using Regex boundaries to fix buggy string.
-buggyMultiline = `tey, ihe light-greon apple
-tangs on ihe greon traa`;
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-// 1) Use ^ to fix the matching at the begining of the string, and right after newline.
-buggyMultiline = buggyMultiline.replace(/^t/gim,'h');
-console.log(1, buggyMultiline); // fix 'tey', 'tangs' => 'hey', 'hangs'. Avoid 'traa'.
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-// 2) Use $ to fix matching at the end of the text.
-buggyMultiline = buggyMultiline.replace(/aa$/gim,'ee.');
-console.log(2, buggyMultiline); // fix  'traa' => 'tree'.
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-// 3) Use \b to match characters right on border between a word and a space.
-buggyMultiline = buggyMultiline.replace(/\bi/gim,'t');
-console.log(3, buggyMultiline); // fix  'ihe' but does not touch 'light'.
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-// 4) Use \B to match characters inside borders of an entity.
-fixedMultiline = buggyMultiline.replace(/\Bo/gim,'e');
-console.log(4, fixedMultiline); // fix  'greon' but does not touch 'on'.
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Matching the beginning of an input using a ^ control character

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입력 시작시 일치를 위해 ^를 사용하십시오. 이 예에서는 /^A/ regex로 'A'로 시작하는 결과를 얻습니다. 여기서 ^는 한 가지 역할 만합니다. 적절한 결과를 보기위해 화살표 함수가있는 필터 메소드를 사용합니다.

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let fruits = ["Apple", "Watermelon", "Orange", "Avocado", "Strawberry"];
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-// Select fruits started with 'A' by /^A/ Regex.
-// Here '^' control symbol used only in one role: Matching begining of an input.
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-let fruitsStartsWithA = fruits.filter(fruit => /^A/.test(fruit));
-console.log(fruitsStartsWithA); // [ 'Apple', 'Avocado' ]
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두 번째 예제에서 ^는 두 가지 모두에 사용됩니다 : 입력의 일치 시작점, 그룹에서 사용될 때 부정 또는 보완 문자 세트.

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let fruits = ["Apple", "Watermelon", "Orange", "Avocado", "Strawberry"];
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-// Selecting fruits that dose not start by 'A' by a /^[^A]/ regex.
-// In this example, two meanings of '^' control symbol are represented:
-// 1) Matching begining of the input
-// 2) A negated or complemented character set: [^A]
-// That is, it matches anything that is not enclosed in the brackets.
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-let fruitsStartsWithNotA = fruits.filter(fruit => /^[^A]/.test(fruit));
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-console.log(fruitsStartsWithNotA); // [ 'Watermelon', 'Orange', 'Strawberry' ]
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Matching a word boundary

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let fruitsWithDescription = ["Red apple", "Orange orange", "Green Avocado"];
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-// Select descriptions that contains 'en' or 'ed' words endings:
-let enEdSelection = fruitsWithDescription.filter(descr => /(en|ed)\b/.test(descr));
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-console.log(enEdSelection); // [ 'Red apple', 'Green Avocado' ]
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Lookahead assertion

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// JS Lookahead assertion x(?=y)
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-let regex = /First(?= test)/g;
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-console.log('First test'.match(regex)); // [ 'First' ]
-console.log('First peach'.match(regex)); // null
-console.log('This is a First test in a year.'.match(regex)); // [ 'First' ]
-console.log('This is a First peach in a month.'.match(regex)); // null
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Basic negative lookahead assertion

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For example, /\d+(?!\.)/ matches a number only if it is not followed by a decimal point. /\d+(?!\.)/.exec('3.141') matches "141" but not "3.

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console.log(/\d+(?!\.)/g.exec('3.141')); // [ '141', index: 2, input: '3.141' ]
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Different meaning of '?!' combination usage in Assertions and  Ranges 

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Different meaning of ?! combination usage in Assertions /x(?!y)/ and Ranges [^?!].

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let orangeNotLemon = "Do you want to have an orange? Yes, I do not want to have a lemon!";
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-// Different meaning of '?!' combination usage in Assertions /x(?!y)/ and  Ranges /[^?!]/
-let selectNotLemonRegex = /[^?!]+have(?! a lemon)[^?!]+[?!]/gi
-console.log(orangeNotLemon.match(selectNotLemonRegex)); // [ 'Do you want to have an orange?' ]
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-let selectNotOrangeRegex = /[^?!]+have(?! an orange)[^?!]+[?!]/gi
-console.log(orangeNotLemon.match(selectNotOrangeRegex)); // [ ' Yes, I do not want to have a lemon!' ]
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Lookbehind assertion

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let oranges = ['ripe orange A ', 'green orange B', 'ripe orange C',];
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-let ripe_oranges = oranges.filter( fruit => fruit.match(/(?<=ripe )orange/));
-console.log(ripe_oranges); // [ 'ripe orange A ', 'ripe orange C' ]
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Specifications

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SpecificationStatusComment
{{SpecName('ESDraft', '#sec-assertion', 'RegExp: Assertions')}}{{Spec2('ESDraft')}}
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Browser compatibility

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For browser compatibility information, check out the main Regular Expressions compatibility table.

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See also

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