Polyfill for String.codePointAt for ECMAScript 5.1 browsers

LICENSE.txt

@@ -24,3 +24,28 @@ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+=====
+
+MIT License for codepointat.js from https://git.io/codepointat
+
+Copyright Mathias Bynens <https://mathiasbynens.be/>
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

runtime/JavaScript/src/antlr4/index.js

@@ -3,6 +3,7 @@
  * can be found in the LICENSE.txt file in the project root.
  */
 exports.atn = require('./atn/index');
+exports.codepointat = require('./polyfills/codepointat');
 exports.dfa = require('./dfa/index');
 exports.tree = require('./tree/index');
 exports.error = require('./error/index');

runtime/JavaScript/src/antlr4/polyfills/codepointat.js

@@ -0,0 +1,54 @@
+/*! https://mths.be/codepointat v0.2.0 by @mathias */
+if (!String.prototype.codePointAt) {
+	(function() {
+		'use strict'; // needed to support `apply`/`call` with `undefined`/`null`
+		var defineProperty = (function() {
+			// IE 8 only supports `Object.defineProperty` on DOM elements
+			try {
+				var object = {};
+				var $defineProperty = Object.defineProperty;
+				var result = $defineProperty(object, object, object) && $defineProperty;
+			} catch(error) {}
+			return result;
+		}());
+		var codePointAt = function(position) {
+			if (this == null) {
+				throw TypeError();
+			}
+			var string = String(this);
+			var size = string.length;
+			// `ToInteger`
+			var index = position ? Number(position) : 0;
+			if (index != index) { // better `isNaN`
+				index = 0;
+			}
+			// Account for out-of-bounds indices:
+			if (index < 0 || index >= size) {
+				return undefined;
+			}
+			// Get the first code unit
+			var first = string.charCodeAt(index);
+			var second;
+			if ( // check if it’s the start of a surrogate pair
+				first >= 0xD800 && first <= 0xDBFF && // high surrogate
+				size > index + 1 // there is a next code unit
+			) {
+				second = string.charCodeAt(index + 1);
+				if (second >= 0xDC00 && second <= 0xDFFF) { // low surrogate
+					// https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
+					return (first - 0xD800) * 0x400 + second - 0xDC00 + 0x10000;
+				}
+			}
+			return first;
+		};
+		if (defineProperty) {
+			defineProperty(String.prototype, 'codePointAt', {
+				'value': codePointAt,
+				'configurable': true,
+				'writable': true
+			});
+		} else {
+			String.prototype.codePointAt = codePointAt;
+		}
+	}());
+}