String.fromCodePoint()

String.fromCodePoint() 静的メソッドは指定されたコードポイントのシーケンスを使って生成された文字列を返します。

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構文

String.fromCodePoint(num1[, ...[, numN]])

引数

num1, ..., numN

コードポイントのシーケンスです。

戻り値

指定されたコードポイントのシーケンスを使って生成された文字列です。

例外

• 無効な Unicode コードポイントを与えられた場合、RangeError （例: "RangeError: NaN is not a valid code point" ）がスローされます。

説明

このメソッドは String オブジェクトではなく文字列を返します。

fromCodePoint() メソッドは String の静的なメソッドなので、自ら生成した String オブジェクトのメソッドとしてではなく、常に String.fromCodePoint() として使用してください。

例

fromCodePoint() を使う

String.fromCodePoint(42);       // "*"
String.fromCodePoint(65, 90);   // "AZ"
String.fromCodePoint(0x404);    // "\u0404"
String.fromCodePoint(0x2F804);  // "\uD87E\uDC04"
String.fromCodePoint(194564);   // "\uD87E\uDC04"
String.fromCodePoint(0x1D306, 0x61, 0x1D307) // "\uD834\uDF06a\uD834\uDF07"

String.fromCodePoint('_');      // RangeError
String.fromCodePoint(Infinity); // RangeError
String.fromCodePoint(-1);       // RangeError
String.fromCodePoint(3.14);     // RangeError
String.fromCodePoint(3e-2);     // RangeError
String.fromCodePoint(NaN);      // RangeError

// String.fromCharCode() alone cannot get the character at such a high code point
// The following, on the other hand, can return a 4-byte character as well as the
// usual 2-byte ones (i.e., it can return a single character which actually has
// a string length of 2 instead of 1!)
console.log(String.fromCodePoint(0x2F804)); // or 194564 in decimal

ポリフィル

String.fromCodePoint メソッドは ECMAScript 2015 で追加されました。まだすべての Web ブラウザーや環境でサポートされていないかもしれません。互換性のために次のコードを使用してください。:

if (!String.fromCodePoint) (function(stringFromCharCode) {
    var fromCodePoint = function(_) {
      var codeUnits = [], codeLen = 0, result = "";
      for (var index=0, len = arguments.length; index !== len; ++index) {
        var codePoint = +arguments[index];
        // correctly handles all cases including `NaN`, `-Infinity`, `+Infinity`
        // The surrounding `!(...)` is required to correctly handle `NaN` cases
        // The (codePoint>>>0) === codePoint clause handles decimals and negatives
        if (!(codePoint < 0x10FFFF && (codePoint>>>0) === codePoint))
          throw RangeError("Invalid code point: " + codePoint);
        if (codePoint <= 0xFFFF) { // BMP code point
          codeLen = codeUnits.push(codePoint);
        } else { // Astral code point; split in surrogate halves
          // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
          codePoint -= 0x10000;
          codeLen = codeUnits.push(
            (codePoint >> 10) + 0xD800,  // highSurrogate
            (codePoint % 0x400) + 0xDC00 // lowSurrogate
          );
        }
        if (codeLen >= 0x3fff) {
          result += stringFromCharCode.apply(null, codeUnits);
          codeUnits.length = 0;
        }
      }
      return result + stringFromCharCode.apply(null, codeUnits);
    };
    try { // IE 8 only supports `Object.defineProperty` on DOM elements
      Object.defineProperty(String, "fromCodePoint", {
        "value": fromCodePoint, "configurable": true, "writable": true
      });
    } catch(e) {
      String.fromCodePoint = fromCodePoint;
    }
}(String.fromCharCode));

仕様

ブラウザー実装状況

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

関連情報

• String.fromCharCode()
• String.prototype.charAt()
• String.prototype.codePointAt()
• String.prototype.charCodeAt()