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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:42:17 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:42:17 -0500 |
commit | da78a9e329e272dedb2400b79a3bdeebff387d47 (patch) | |
tree | e6ef8aa7c43556f55ddfe031a01cf0a8fa271bfe /files/ko/web/javascript/reference/global_objects/string/charat | |
parent | 1109132f09d75da9a28b649c7677bb6ce07c40c0 (diff) | |
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diff --git a/files/ko/web/javascript/reference/global_objects/string/charat/index.html b/files/ko/web/javascript/reference/global_objects/string/charat/index.html new file mode 100644 index 0000000000..a5a68c03be --- /dev/null +++ b/files/ko/web/javascript/reference/global_objects/string/charat/index.html @@ -0,0 +1,260 @@ +--- +title: String.prototype.charAt() +slug: Web/JavaScript/Reference/Global_Objects/String/charAt +tags: + - JavaScript + - Method + - Prototype + - Reference + - String +translation_of: Web/JavaScript/Reference/Global_Objects/String/charAt +--- +<div>{{JSRef}}</div> + +<p><strong>charAt() </strong>함수는 문자열에서 특정 인덱스에 위치하는 유니코드 단일문자를 반환합니다. </p> + +<div>{{EmbedInteractiveExample("pages/js/string-charat.html")}}</div> + + + +<h2 id="구문">구문</h2> + +<pre class="syntaxbox"><code><var>str</var>.charAt(<var>index</var>)</code></pre> + +<h3 id="매개변수">매개변수</h3> + +<ul> + <li>0과 문자열의 길이 - 1 사이의 정수값. </li> + <li>인자를 생략하면 기본값으로 0를 설정되고 첫 문자를 반환한다. </li> +</ul> + +<dl> + <dt><code>index</code></dt> +</dl> + +<h3 id="반환_값">반환 값</h3> + +<ul> + <li>지정된 인덱스에 해당하는 유니코드 단일문자를 반환한다.</li> + <li>만약 인덱스가 문자열 길이보다 큰 경우 빈 문자열 (예) " " 을 반환한다. </li> +</ul> + +<h2 id="설명">설명</h2> + +<p>문자열 내의 문자는 왼쪽에서 오른쪽으로 순번(인덱스)이 매겨집니다. 첫 번째 문자의 순번은 0, 그리고 <code>stringName</code> 이라는 이름을 가진 문자열의 마지막 문자 순번은 <code>stringName.length - 1 </code>입니다. <code>index</code>가 문자열 길이를 벗어나면 빈 문자열을 반환하게 됩니다.</p> + +<p><code>index</code>를 제공하지 않으면 기본값은 0입니다.</p> + +<h2 id="예제">예제</h2> + +<h3 id="문자열_내의_다른_위치에_있는_문자들을_출력하기">문자열 내의 다른 위치에 있는 문자들을 출력하기</h3> + +<p>아래 예제는 문자열 <code>"Brave new world"</code>의 다른 위치에 있는 문자들을 출력합니다.</p> + +<pre class="brush: js">var anyString = 'Brave new world'; +console.log("The character at index 0 is '" + anyString.charAt() + "'"); +// No index was provided, used 0 as default + +console.log("The character at index 0 is '" + anyString.charAt(0) + "'"); +console.log("The character at index 1 is '" + anyString.charAt(1) + "'"); +console.log("The character at index 2 is '" + anyString.charAt(2) + "'"); +console.log("The character at index 3 is '" + anyString.charAt(3) + "'"); +console.log("The character at index 4 is '" + anyString.charAt(4) + "'"); +console.log("The character at index 999 is '" + anyString.charAt(999) + "'"); +</pre> + +<p>프로그램의 실행 결과는 아래와 같습니다.</p> + +<pre class="brush: js">The character at index 0 is 'B' +The character at index 1 is 'r' +The character at index 2 is 'a' +The character at index 3 is 'v' +The character at index 4 is 'e' +The character at index 999 is '' +</pre> + +<h3 id="문자열_내의_모든_문자_얻기">문자열 내의 모든 문자 얻기</h3> + +<p>아래 예제는 문자열 전체를 순회하며 각 문자가 완전한지 확인하는 프로그램입니다. 심지어 <a href="https://ko.wikipedia.org/wiki/%EC%9C%A0%EB%8B%88%EC%BD%94%EB%93%9C_%ED%8F%89%EB%A9%B4">기본 다국어 평면(Basic Multilingual Plane)</a>에 포함되지 않은 문자들이 포함되어 있다고 하더라도 잘 동작합니다. </p> + +<pre class="brush: js">var str = 'A \uD87E\uDC04 Z'; // 기본 다국어 평면에 포함되지 않는 문자를 사용합니다. +for (var i = 0, chr; i < str.length; i++) { + if ((chr = getWholeChar(str, i)) === false) { + continue; + } + // Adapt this line at the top of each loop, passing in the whole string and + // the current iteration and returning a variable to represent the + // individual character + + console.log(chr); +} + +function getWholeChar(str, i) { + var code = str.charCodeAt(i); + + if (Number.isNaN(code)) { + return ''; // Position not found + } + if (code < 0xD800 || code > 0xDFFF) { + return str.charAt(i); + } + + // High surrogate (could change last hex to 0xDB7F to treat high private + // surrogates as single characters) + if (0xD800 <= code && code <= 0xDBFF) { + if (str.length <= (i + 1)) { + throw 'High surrogate without following low surrogate'; + } + var next = str.charCodeAt(i + 1); + if (0xDC00 > next || next > 0xDFFF) { + throw 'High surrogate without following low surrogate'; + } + return str.charAt(i) + str.charAt(i + 1); + } + // Low surrogate (0xDC00 <= code && code <= 0xDFFF) + if (i === 0) { + throw 'Low surrogate without preceding high surrogate'; + } + var prev = str.charCodeAt(i - 1); + + // (could change last hex to 0xDB7F to treat high private + // surrogates as single characters) + if (0xD800 > prev || prev > 0xDBFF) { + throw 'Low surrogate without preceding high surrogate'; + } + // We can pass over low surrogates now as the second component + // in a pair which we have already processed + return false; +} +</pre> + +<p><a href="/ko/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment">비구조화 할당</a>을 허용하는 ECMAScript 2016 환경에서는 아래 예제 코드가 더 간결하고, 문자가 <a href="https://ko.wikipedia.org/wiki/UTF-16">서러게이트 페어</a>가 되는 것을 허용할 때는 증가해야 하는 변수를 자동적으로 증가하기에 위의 코드보다 다소 더 유연합니다.</p> + +<pre class="brush: js">var str = 'A\uD87E\uDC04Z'; // We could also use a non-BMP character directly +for (var i = 0, chr; i < str.length; i++) { + [chr, i] = getWholeCharAndI(str, i); + // Adapt this line at the top of each loop, passing in the whole string and + // the current iteration and returning an array with the individual character + // and 'i' value (only changed if a surrogate pair) + + console.log(chr); +} + +function getWholeCharAndI(str, i) { + var code = str.charCodeAt(i); + + if (Number.isNaN(code)) { + return ''; // Position not found + } + if (code < 0xD800 || code > 0xDFFF) { + return [str.charAt(i), i]; // Normal character, keeping 'i' the same + } + + // High surrogate (could change last hex to 0xDB7F to treat high private + // surrogates as single characters) + if (0xD800 <= code && code <= 0xDBFF) { + if (str.length <= (i + 1)) { + throw 'High surrogate without following low surrogate'; + } + var next = str.charCodeAt(i + 1); + if (0xDC00 > next || next > 0xDFFF) { + throw 'High surrogate without following low surrogate'; + } + return [str.charAt(i) + str.charAt(i + 1), i + 1]; + } + // Low surrogate (0xDC00 <= code && code <= 0xDFFF) + if (i === 0) { + throw 'Low surrogate without preceding high surrogate'; + } + var prev = str.charCodeAt(i - 1); + + // (could change last hex to 0xDB7F to treat high private surrogates + // as single characters) + if (0xD800 > prev || prev > 0xDBFF) { + throw 'Low surrogate without preceding high surrogate'; + } + // Return the next character instead (and increment) + return [str.charAt(i + 1), i + 1]; +} +</pre> + +<h3 id="기본다국어평면(Basic-Multilingual-Plane)이_아닌_문자들을_지원하도록_charAt()_수정하기">기본다국어평면(Basic-Multilingual-Plane)이 아닌 문자들을 지원하도록 <code>charAt()</code> 수정하기</h3> + +<p>어떠한 non-BMP 문자들이 나타났는지 호출자가 알 필요가 없기 때문에 non-BMP 문자들을 지원하도록 하는데는 앞의 예제들이 더 자주 사용되지만, 인덱스로 문자를 선택하는데 있어서 문자열 내에 서로게이트 페어들이 하나의 문자들로 처리되길 원한다면, 아래 예제 코드를 사용하면 됩니다.</p> + +<pre class="brush: js">function fixedCharAt(str, idx) { + var ret = ''; + str += ''; + var end = str.length; + + var surrogatePairs = /[\uD800-\uDBFF][\uDC00-\uDFFF]/g; + while ((surrogatePairs.exec(str)) != null) { + var li = surrogatePairs.lastIndex; + if (li - 2 < idx) { + idx++; + } else { + break; + } + } + + if (idx >= end || idx < 0) { + return ''; + } + + ret += str.charAt(idx); + + if (/[\uD800-\uDBFF]/.test(ret) && /[\uDC00-\uDFFF]/.test(str.charAt(idx + 1))) { + // Go one further, since one of the "characters" is part of a surrogate pair + ret += str.charAt(idx + 1); + } + return ret; +} +</pre> + +<h2 id="명세">명세</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status</th> + <th scope="col">Comment</th> + </tr> + <tr> + <td>{{SpecName('ES1')}}</td> + <td>{{Spec2('ES1')}}</td> + <td>Initial definition.</td> + </tr> + <tr> + <td>{{SpecName('ES5.1', '#sec-15.5.4.4', 'String.prototype.charAt')}}</td> + <td>{{Spec2('ES5.1')}}</td> + <td> </td> + </tr> + <tr> + <td>{{SpecName('ES6', '#sec-string.prototype.charat', 'String.prototype.charAt')}}</td> + <td>{{Spec2('ES6')}}</td> + <td> </td> + </tr> + <tr> + <td>{{SpecName('ESDraft', '#sec-string.prototype.charat', 'String.prototype.charAt')}}</td> + <td>{{Spec2('ESDraft')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="브라우저_호환성">브라우저 호환성</h2> + +<p>{{Compat("javascript.builtins.String.charAt")}}</p> + +<h2 id="관련문서">관련문서</h2> + +<ul> + <li>{{jsxref("String.prototype.indexOf()")}}</li> + <li>{{jsxref("String.prototype.lastIndexOf()")}}</li> + <li>{{jsxref("String.prototype.charCodeAt()")}}</li> + <li>{{jsxref("String.prototype.codePointAt()")}}</li> + <li>{{jsxref("String.prototype.split()")}}</li> + <li>{{jsxref("String.fromCodePoint()")}}</li> + <li><a href="https://mathiasbynens.be/notes/javascript-unicode">JavaScript has a Unicode problem – Mathias Bynens</a></li> +</ul> |