sdk/lib/_internal/js_runtime/lib/js_string.dart - sdk.git - Git at Google

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 part of _interceptors;

 /// The interceptor class for [String]. The compiler recognizes this
 /// class as an interceptor, and changes references to [:this:] to
 /// actually use the receiver of the method, which is generated as an extra
 /// argument added to each member.
 class JSString extends Interceptor implements String, JSIndexable {
   const JSString();

   @pragma('dart2js:noInline')
   int codeUnitAt(int index) {
     if (index is! int) throw diagnoseIndexError(this, index);
     if (index < 0) throw diagnoseIndexError(this, index);
     return _codeUnitAt(index);
   }

   int _codeUnitAt(int index) {
     if (index >= length) throw diagnoseIndexError(this, index);
     return JS('JSUInt31', r'#.charCodeAt(#)', this, index);
   }

   Iterable<Match> allMatches(String string, [int start = 0]) {
     checkString(string);
     checkInt(start);
     if (0 > start || start > string.length) {
       throw new RangeError.range(start, 0, string.length);
     }
     return allMatchesInStringUnchecked(this, string, start);
   }

   Match? matchAsPrefix(String string, [int start = 0]) {
     if (start < 0 || start > string.length) {
       throw new RangeError.range(start, 0, string.length);
     }
     if (start + this.length > string.length) return null;
     // TODO(lrn): See if this can be optimized.
     for (int i = 0; i < this.length; i++) {
       if (string.codeUnitAt(start + i) != this.codeUnitAt(i)) {
         return null;
       }
     }
     return new StringMatch(start, string, this);
   }

   String operator +(String other) {
     if (other is! String) throw new ArgumentError.value(other);
     return JS('String', r'# + #', this, other);
   }

   bool endsWith(String other) {
     checkString(other);
     int otherLength = other.length;
     if (otherLength > length) return false;
     return other == substring(length - otherLength);
   }

   String replaceAll(Pattern from, String to) {
     return stringReplaceAllUnchecked(this, from, checkString(to));
   }

   String replaceAllMapped(Pattern from, String Function(Match) convert) {
     return this.splitMapJoin(from, onMatch: convert);
   }

   String splitMapJoin(Pattern from,
       {String Function(Match)? onMatch, String Function(String)? onNonMatch}) {
     return stringReplaceAllFuncUnchecked(this, from, onMatch, onNonMatch);
   }

   String replaceFirst(Pattern from, String to, [int startIndex = 0]) {
     checkString(to);
     checkInt(startIndex);
     RangeError.checkValueInInterval(startIndex, 0, this.length, "startIndex");
     return stringReplaceFirstUnchecked(this, from, to, startIndex);
   }

   String replaceFirstMapped(Pattern from, String replace(Match match),
       [int startIndex = 0]) {
     checkNull(replace);
     checkInt(startIndex);
     RangeError.checkValueInInterval(startIndex, 0, this.length, "startIndex");
     return stringReplaceFirstMappedUnchecked(this, from, replace, startIndex);
   }

   List<String> split(Pattern pattern) {
     checkNull(pattern);
     if (pattern is String) {
       return stringSplitUnchecked(this, pattern);
     } else if (pattern is JSSyntaxRegExp && regExpCaptureCount(pattern) == 0) {
       var re = regExpGetNative(pattern);
       return stringSplitUnchecked(this, re);
     } else {
       return _defaultSplit(pattern);
     }
   }

   String replaceRange(int start, int? end, String replacement) {
     checkString(replacement);
     checkInt(start);
     var e = RangeError.checkValidRange(start, end, this.length);
     checkInt(e);
     return stringReplaceRangeUnchecked(this, start, e, replacement);
   }

   List<String> _defaultSplit(Pattern pattern) {
     List<String> result = <String>[];
     // End of most recent match. That is, start of next part to add to result.
     int start = 0;
     // Length of most recent match.
     // Set >0, so no match on the empty string causes the result to be [""].
     int length = 1;
     for (var match in pattern.allMatches(this)) {
       int matchStart = match.start;
       int matchEnd = match.end;
       length = matchEnd - matchStart;
       if (length == 0 && start == matchStart) {
         // An empty match right after another match is ignored.
         // This includes an empty match at the start of the string.
         continue;
       }
       int end = matchStart;
       result.add(this.substring(start, end));
       start = matchEnd;
     }
     if (start < this.length || length > 0) {
       // An empty match at the end of the string does not cause a "" at the end.
       // A non-empty match ending at the end of the string does add a "".
       result.add(this.substring(start));
     }
     return result;
   }

   bool startsWith(Pattern pattern, [int index = 0]) {
     checkInt(index);
     if (index < 0 || index > this.length) {
       throw new RangeError.range(index, 0, this.length);
     }
     if (pattern is String) {
       String other = pattern;
       int otherLength = other.length;
       int endIndex = index + otherLength;
       if (endIndex > length) return false;
       return other == JS('String', r'#.substring(#, #)', this, index, endIndex);
     }
     return pattern.matchAsPrefix(this, index) != null;
   }

   @pragma('dart2js:noInline')
   String substring(int start, [int? end]) {
     checkInt(start);
     end = RangeError.checkValidRange(start, end, this.length);
     return JS('String', r'#.substring(#, #)', this, start, end);
   }

   String toLowerCase() {
     return JS('returns:String;effects:none;depends:none;throws:null(1)',
         r'#.toLowerCase()', this);
   }

   String toUpperCase() {
     return JS('returns:String;effects:none;depends:none;throws:null(1)',
         r'#.toUpperCase()', this);
   }

   // Characters with Whitespace property (Unicode 6.3).
   // 0009..000D    ; White_Space # Cc       <control-0009>..<control-000D>
   // 0020          ; White_Space # Zs       SPACE
   // 0085          ; White_Space # Cc       <control-0085>
   // 00A0          ; White_Space # Zs       NO-BREAK SPACE
   // 1680          ; White_Space # Zs       OGHAM SPACE MARK
   // 2000..200A    ; White_Space # Zs       EN QUAD..HAIR SPACE
   // 2028          ; White_Space # Zl       LINE SEPARATOR
   // 2029          ; White_Space # Zp       PARAGRAPH SEPARATOR
   // 202F          ; White_Space # Zs       NARROW NO-BREAK SPACE
   // 205F          ; White_Space # Zs       MEDIUM MATHEMATICAL SPACE
   // 3000          ; White_Space # Zs       IDEOGRAPHIC SPACE
   //
   // BOM: 0xFEFF
   static bool _isWhitespace(int codeUnit) {
     // Most codeUnits should be less than 256. Special case with a smaller
     // switch.
     if (codeUnit < 256) {
       switch (codeUnit) {
         case 0x09:
         case 0x0A:
         case 0x0B:
         case 0x0C:
         case 0x0D:
         case 0x20:
         case 0x85:
         case 0xA0:
           return true;
         default:
           return false;
       }
     }
     switch (codeUnit) {
       case 0x1680:
       case 0x2000:
       case 0x2001:
       case 0x2002:
       case 0x2003:
       case 0x2004:
       case 0x2005:
       case 0x2006:
       case 0x2007:
       case 0x2008:
       case 0x2009:
       case 0x200A:
       case 0x2028:
       case 0x2029:
       case 0x202F:
       case 0x205F:
       case 0x3000:
       case 0xFEFF:
         return true;
       default:
         return false;
     }
   }

   /// Finds the index of the first non-whitespace character, or the
   /// end of the string. Start looking at position [index].
   static int _skipLeadingWhitespace(String string, int index) {
     const int SPACE = 0x20;
     const int CARRIAGE_RETURN = 0x0D;
     while (index < string.length) {
       int codeUnit = string.codeUnitAt(index);
       if (codeUnit != SPACE &&
           codeUnit != CARRIAGE_RETURN &&
           !_isWhitespace(codeUnit)) {
         break;
       }
       index++;
     }
     return index;
   }

   /// Finds the index after the last non-whitespace character, or 0.
   /// Start looking at position [index - 1].
   static int _skipTrailingWhitespace(String string, int index) {
     const int SPACE = 0x20;
     const int CARRIAGE_RETURN = 0x0D;
     while (index > 0) {
       int codeUnit = string.codeUnitAt(index - 1);
       if (codeUnit != SPACE &&
           codeUnit != CARRIAGE_RETURN &&
           !_isWhitespace(codeUnit)) {
         break;
       }
       index--;
     }
     return index;
   }

   // Dart2js can't use JavaScript trim directly,
   // because JavaScript does not trim
   // the NEXT LINE (NEL) character (0x85).
   String trim() {
     const int NEL = 0x85;

     // Start by doing JS trim. Then check if it leaves a NEL at
     // either end of the string.
     String result = JS('String', '#.trim()', this);
     if (result.length == 0) return result;
     int firstCode = result.codeUnitAt(0);
     int startIndex = 0;
     if (firstCode == NEL) {
       startIndex = _skipLeadingWhitespace(result, 1);
       if (startIndex == result.length) return "";
     }

     int endIndex = result.length;
     // We know that there is at least one character that is non-whitespace.
     // Therefore we don't need to verify that endIndex > startIndex.
     int lastCode = result.codeUnitAt(endIndex - 1);
     if (lastCode == NEL) {
       endIndex = _skipTrailingWhitespace(result, endIndex - 1);
     }
     if (startIndex == 0 && endIndex == result.length) return result;
     return JS('String', r'#.substring(#, #)', result, startIndex, endIndex);
   }

   // Dart2js can't use JavaScript trimLeft directly,
   // because it is not in ES5, so not every browser implements it,
   // and because those that do will not trim the NEXT LINE character (0x85).
   String trimLeft() {
     const int NEL = 0x85;

     // Start by doing JS trim. Then check if it leaves a NEL at
     // the beginning of the string.
     String result;
     int startIndex = 0;
     if (JS('bool', 'typeof #.trimLeft != "undefined"', this)) {
       result = JS('String', '#.trimLeft()', this);
       if (result.length == 0) return result;
       int firstCode = result.codeUnitAt(0);
       if (firstCode == NEL) {
         startIndex = _skipLeadingWhitespace(result, 1);
       }
     } else {
       result = this;
       startIndex = _skipLeadingWhitespace(this, 0);
     }
     if (startIndex == 0) return result;
     if (startIndex == result.length) return "";
     return JS('String', r'#.substring(#)', result, startIndex);
   }

   // Dart2js can't use JavaScript trimRight directly,
   // because it is not in ES5 and because JavaScript does not trim
   // the NEXT LINE character (0x85).
   String trimRight() {
     const int NEL = 0x85;

     // Start by doing JS trim. Then check if it leaves a NEL or BOM at
     // the end of the string.
     String result;
     int endIndex;
     // trimRight is implemented by Firefox and Chrome/Blink,
     // so use it if it is there.
     if (JS('bool', 'typeof #.trimRight != "undefined"', this)) {
       result = JS('String', '#.trimRight()', this);
       endIndex = result.length;
       if (endIndex == 0) return result;
       int lastCode = result.codeUnitAt(endIndex - 1);
       if (lastCode == NEL) {
         endIndex = _skipTrailingWhitespace(result, endIndex - 1);
       }
     } else {
       result = this;
       endIndex = _skipTrailingWhitespace(this, this.length);
     }

     if (endIndex == result.length) return result;
     if (endIndex == 0) return "";
     return JS('String', r'#.substring(#, #)', result, 0, endIndex);
   }

   String operator *(int times) {
     if (0 >= times) return ''; // Unnecessary but hoists argument type check.
     if (times == 1 || this.length == 0) return this;
     if (times != JS('JSUInt32', '# >>> 0', times)) {
       // times >= 2^32. We can't create a string that big.
       throw const OutOfMemoryError();
     }
     var result = '';
     String s = this;
     while (true) {
       if (times & 1 == 1) result = s + result;
       times = JS('JSUInt31', '# >>> 1', times);
       if (times == 0) break;
       s += s;
     }
     return result;
   }

   String padLeft(int width, [String padding = ' ']) {
     int delta = width - this.length;
     if (delta <= 0) return this;
     return padding * delta + this;
   }

   String padRight(int width, [String padding = ' ']) {
     int delta = width - this.length;
     if (delta <= 0) return this;
     return this + padding * delta;
   }

   List<int> get codeUnits => new CodeUnits(this);

   Runes get runes => new Runes(this);

   int indexOf(Pattern pattern, [int start = 0]) {
     checkNull(pattern);
     if (start is! int) throw argumentErrorValue(start);
     if (start < 0 || start > this.length) {
       throw new RangeError.range(start, 0, this.length);
     }
     if (pattern is String) {
       return stringIndexOfStringUnchecked(this, pattern, start);
     }
     if (pattern is JSSyntaxRegExp) {
       JSSyntaxRegExp re = pattern;
       Match? match = firstMatchAfter(re, this, start);
       return (match == null) ? -1 : match.start;
     }
     for (int i = start; i <= this.length; i++) {
       if (pattern.matchAsPrefix(this, i) != null) return i;
     }
     return -1;
   }

   int lastIndexOf(Pattern pattern, [int? start]) {
     checkNull(pattern);
     if (start == null) {
       start = length;
     } else if (start is! int) {
       throw argumentErrorValue(start);
     } else if (start < 0 || start > this.length) {
       throw new RangeError.range(start, 0, this.length);
     }
     if (pattern is String) {
       String other = pattern;
       if (start + other.length > this.length) {
         start = this.length - other.length;
       }
       return stringLastIndexOfUnchecked(this, other, start);
     }
     for (int i = start; i >= 0; i--) {
       if (pattern.matchAsPrefix(this, i) != null) return i;
     }
     return -1;
   }

   bool contains(Pattern other, [int startIndex = 0]) {
     checkNull(other);
     if (startIndex < 0 || startIndex > this.length) {
       throw new RangeError.range(startIndex, 0, this.length);
     }
     return stringContainsUnchecked(this, other, startIndex);
   }

   bool get isEmpty => length == 0;

   bool get isNotEmpty => !isEmpty;

   int compareTo(String other) {
     if (other is! String) throw argumentErrorValue(other);
     return this == other
         ? 0
         : JS('bool', r'# < #', this, other)
             ? -1
             : 1;
   }

   // Note: if you change this, also change the function [S].
   String toString() => this;

   /// This is the [Jenkins hash function][1] but using masking to keep
   /// values in SMI range.
   ///
   /// [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function
   int get hashCode {
     // TODO(ahe): This method shouldn't have to use JS. Update when our
     // optimizations are smarter.
     int hash = 0;
     for (int i = 0; i < length; i++) {
       hash = 0x1fffffff & (hash + JS<int>('int', r'#.charCodeAt(#)', this, i));
       hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
       hash = JS('int', '# ^ (# >> 6)', hash, hash);
     }
     hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
     hash = JS<int>('int', '# ^ (# >> 11)', hash, hash);
     return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
   }

   Type get runtimeType => String;

   int get length => JS('int', r'#.length', this);

   String operator [](int index) {
     if (index is! int) throw diagnoseIndexError(this, index);
     // This form of the range test correctly rejects NaN.
     if (!(index >= 0 && index < length)) throw diagnoseIndexError(this, index);
     return JS('String', '#[#]', this, index);
   }
 }
	// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	part of _interceptors;

	/// The interceptor class for [String]. The compiler recognizes this
	/// class as an interceptor, and changes references to [:this:] to
	/// actually use the receiver of the method, which is generated as an extra
	/// argument added to each member.
	class JSString extends Interceptor implements String, JSIndexable {
	const JSString();

	@pragma('dart2js:noInline')
	int codeUnitAt(int index) {
	if (index is! int) throw diagnoseIndexError(this, index);
	if (index < 0) throw diagnoseIndexError(this, index);
	return _codeUnitAt(index);
	}

	int _codeUnitAt(int index) {
	if (index >= length) throw diagnoseIndexError(this, index);
	return JS('JSUInt31', r'#.charCodeAt(#)', this, index);
	}

	Iterable<Match> allMatches(String string, [int start = 0]) {
	checkString(string);
	checkInt(start);
	if (0 > start \|\| start > string.length) {
	throw new RangeError.range(start, 0, string.length);
	}
	return allMatchesInStringUnchecked(this, string, start);
	}

	Match? matchAsPrefix(String string, [int start = 0]) {
	if (start < 0 \|\| start > string.length) {
	throw new RangeError.range(start, 0, string.length);
	}
	if (start + this.length > string.length) return null;
	// TODO(lrn): See if this can be optimized.
	for (int i = 0; i < this.length; i++) {
	if (string.codeUnitAt(start + i) != this.codeUnitAt(i)) {
	return null;
	}
	}
	return new StringMatch(start, string, this);
	}

	String operator +(String other) {
	if (other is! String) throw new ArgumentError.value(other);
	return JS('String', r'# + #', this, other);
	}

	bool endsWith(String other) {
	checkString(other);
	int otherLength = other.length;
	if (otherLength > length) return false;
	return other == substring(length - otherLength);
	}

	String replaceAll(Pattern from, String to) {
	return stringReplaceAllUnchecked(this, from, checkString(to));
	}

	String replaceAllMapped(Pattern from, String Function(Match) convert) {
	return this.splitMapJoin(from, onMatch: convert);
	}

	String splitMapJoin(Pattern from,
	{String Function(Match)? onMatch, String Function(String)? onNonMatch}) {
	return stringReplaceAllFuncUnchecked(this, from, onMatch, onNonMatch);
	}

	String replaceFirst(Pattern from, String to, [int startIndex = 0]) {
	checkString(to);
	checkInt(startIndex);
	RangeError.checkValueInInterval(startIndex, 0, this.length, "startIndex");
	return stringReplaceFirstUnchecked(this, from, to, startIndex);
	}

	String replaceFirstMapped(Pattern from, String replace(Match match),
	[int startIndex = 0]) {
	checkNull(replace);
	checkInt(startIndex);
	RangeError.checkValueInInterval(startIndex, 0, this.length, "startIndex");
	return stringReplaceFirstMappedUnchecked(this, from, replace, startIndex);
	}

	List<String> split(Pattern pattern) {
	checkNull(pattern);
	if (pattern is String) {
	return stringSplitUnchecked(this, pattern);
	} else if (pattern is JSSyntaxRegExp && regExpCaptureCount(pattern) == 0) {
	var re = regExpGetNative(pattern);
	return stringSplitUnchecked(this, re);
	} else {
	return _defaultSplit(pattern);
	}
	}

	String replaceRange(int start, int? end, String replacement) {
	checkString(replacement);
	checkInt(start);
	var e = RangeError.checkValidRange(start, end, this.length);
	checkInt(e);
	return stringReplaceRangeUnchecked(this, start, e, replacement);
	}

	List<String> _defaultSplit(Pattern pattern) {
	List<String> result = <String>[];
	// End of most recent match. That is, start of next part to add to result.
	int start = 0;
	// Length of most recent match.
	// Set >0, so no match on the empty string causes the result to be [""].
	int length = 1;
	for (var match in pattern.allMatches(this)) {
	int matchStart = match.start;
	int matchEnd = match.end;
	length = matchEnd - matchStart;
	if (length == 0 && start == matchStart) {
	// An empty match right after another match is ignored.
	// This includes an empty match at the start of the string.
	continue;
	}
	int end = matchStart;
	result.add(this.substring(start, end));
	start = matchEnd;
	}
	if (start < this.length \|\| length > 0) {
	// An empty match at the end of the string does not cause a "" at the end.
	// A non-empty match ending at the end of the string does add a "".
	result.add(this.substring(start));
	}
	return result;
	}

	bool startsWith(Pattern pattern, [int index = 0]) {
	checkInt(index);
	if (index < 0 \|\| index > this.length) {
	throw new RangeError.range(index, 0, this.length);
	}
	if (pattern is String) {
	String other = pattern;
	int otherLength = other.length;
	int endIndex = index + otherLength;
	if (endIndex > length) return false;
	return other == JS('String', r'#.substring(#, #)', this, index, endIndex);
	}
	return pattern.matchAsPrefix(this, index) != null;
	}

	@pragma('dart2js:noInline')
	String substring(int start, [int? end]) {
	checkInt(start);
	end = RangeError.checkValidRange(start, end, this.length);
	return JS('String', r'#.substring(#, #)', this, start, end);
	}

	String toLowerCase() {
	return JS('returns:String;effects:none;depends:none;throws:null(1)',
	r'#.toLowerCase()', this);
	}

	String toUpperCase() {
	return JS('returns:String;effects:none;depends:none;throws:null(1)',
	r'#.toUpperCase()', this);
	}

	// Characters with Whitespace property (Unicode 6.3).
	// 0009..000D ; White_Space # Cc <control-0009>..<control-000D>
	// 0020 ; White_Space # Zs SPACE
	// 0085 ; White_Space # Cc <control-0085>
	// 00A0 ; White_Space # Zs NO-BREAK SPACE
	// 1680 ; White_Space # Zs OGHAM SPACE MARK
	// 2000..200A ; White_Space # Zs EN QUAD..HAIR SPACE
	// 2028 ; White_Space # Zl LINE SEPARATOR
	// 2029 ; White_Space # Zp PARAGRAPH SEPARATOR
	// 202F ; White_Space # Zs NARROW NO-BREAK SPACE
	// 205F ; White_Space # Zs MEDIUM MATHEMATICAL SPACE
	// 3000 ; White_Space # Zs IDEOGRAPHIC SPACE
	//
	// BOM: 0xFEFF
	static bool _isWhitespace(int codeUnit) {
	// Most codeUnits should be less than 256. Special case with a smaller
	// switch.
	if (codeUnit < 256) {
	switch (codeUnit) {
	case 0x09:
	case 0x0A:
	case 0x0B:
	case 0x0C:
	case 0x0D:
	case 0x20:
	case 0x85:
	case 0xA0:
	return true;
	default:
	return false;
	}
	}
	switch (codeUnit) {
	case 0x1680:
	case 0x2000:
	case 0x2001:
	case 0x2002:
	case 0x2003:
	case 0x2004:
	case 0x2005:
	case 0x2006:
	case 0x2007:
	case 0x2008:
	case 0x2009:
	case 0x200A:
	case 0x2028:
	case 0x2029:
	case 0x202F:
	case 0x205F:
	case 0x3000:
	case 0xFEFF:
	return true;
	default:
	return false;
	}
	}

	/// Finds the index of the first non-whitespace character, or the
	/// end of the string. Start looking at position [index].
	static int _skipLeadingWhitespace(String string, int index) {
	const int SPACE = 0x20;
	const int CARRIAGE_RETURN = 0x0D;
	while (index < string.length) {
	int codeUnit = string.codeUnitAt(index);
	if (codeUnit != SPACE &&
	codeUnit != CARRIAGE_RETURN &&
	!_isWhitespace(codeUnit)) {
	break;
	}
	index++;
	}
	return index;
	}

	/// Finds the index after the last non-whitespace character, or 0.
	/// Start looking at position [index - 1].
	static int _skipTrailingWhitespace(String string, int index) {
	const int SPACE = 0x20;
	const int CARRIAGE_RETURN = 0x0D;
	while (index > 0) {
	int codeUnit = string.codeUnitAt(index - 1);
	if (codeUnit != SPACE &&
	codeUnit != CARRIAGE_RETURN &&
	!_isWhitespace(codeUnit)) {
	break;
	}
	index--;
	}
	return index;
	}

	// Dart2js can't use JavaScript trim directly,
	// because JavaScript does not trim
	// the NEXT LINE (NEL) character (0x85).
	String trim() {
	const int NEL = 0x85;

	// Start by doing JS trim. Then check if it leaves a NEL at
	// either end of the string.
	String result = JS('String', '#.trim()', this);
	if (result.length == 0) return result;
	int firstCode = result.codeUnitAt(0);
	int startIndex = 0;
	if (firstCode == NEL) {
	startIndex = _skipLeadingWhitespace(result, 1);
	if (startIndex == result.length) return "";
	}

	int endIndex = result.length;
	// We know that there is at least one character that is non-whitespace.
	// Therefore we don't need to verify that endIndex > startIndex.
	int lastCode = result.codeUnitAt(endIndex - 1);
	if (lastCode == NEL) {
	endIndex = _skipTrailingWhitespace(result, endIndex - 1);
	}
	if (startIndex == 0 && endIndex == result.length) return result;
	return JS('String', r'#.substring(#, #)', result, startIndex, endIndex);
	}

	// Dart2js can't use JavaScript trimLeft directly,
	// because it is not in ES5, so not every browser implements it,
	// and because those that do will not trim the NEXT LINE character (0x85).
	String trimLeft() {
	const int NEL = 0x85;

	// Start by doing JS trim. Then check if it leaves a NEL at
	// the beginning of the string.
	String result;
	int startIndex = 0;
	if (JS('bool', 'typeof #.trimLeft != "undefined"', this)) {
	result = JS('String', '#.trimLeft()', this);
	if (result.length == 0) return result;
	int firstCode = result.codeUnitAt(0);
	if (firstCode == NEL) {
	startIndex = _skipLeadingWhitespace(result, 1);
	}
	} else {
	result = this;
	startIndex = _skipLeadingWhitespace(this, 0);
	}
	if (startIndex == 0) return result;
	if (startIndex == result.length) return "";
	return JS('String', r'#.substring(#)', result, startIndex);
	}

	// Dart2js can't use JavaScript trimRight directly,
	// because it is not in ES5 and because JavaScript does not trim
	// the NEXT LINE character (0x85).
	String trimRight() {
	const int NEL = 0x85;

	// Start by doing JS trim. Then check if it leaves a NEL or BOM at
	// the end of the string.
	String result;
	int endIndex;
	// trimRight is implemented by Firefox and Chrome/Blink,
	// so use it if it is there.
	if (JS('bool', 'typeof #.trimRight != "undefined"', this)) {
	result = JS('String', '#.trimRight()', this);
	endIndex = result.length;
	if (endIndex == 0) return result;
	int lastCode = result.codeUnitAt(endIndex - 1);
	if (lastCode == NEL) {
	endIndex = _skipTrailingWhitespace(result, endIndex - 1);
	}
	} else {
	result = this;
	endIndex = _skipTrailingWhitespace(this, this.length);
	}

	if (endIndex == result.length) return result;
	if (endIndex == 0) return "";
	return JS('String', r'#.substring(#, #)', result, 0, endIndex);
	}

	String operator *(int times) {
	if (0 >= times) return ''; // Unnecessary but hoists argument type check.
	if (times == 1 \|\| this.length == 0) return this;
	if (times != JS('JSUInt32', '# >>> 0', times)) {
	// times >= 2^32. We can't create a string that big.
	throw const OutOfMemoryError();
	}
	var result = '';
	String s = this;
	while (true) {
	if (times & 1 == 1) result = s + result;
	times = JS('JSUInt31', '# >>> 1', times);
	if (times == 0) break;
	s += s;
	}
	return result;
	}

	String padLeft(int width, [String padding = ' ']) {
	int delta = width - this.length;
	if (delta <= 0) return this;
	return padding * delta + this;
	}

	String padRight(int width, [String padding = ' ']) {
	int delta = width - this.length;
	if (delta <= 0) return this;
	return this + padding * delta;
	}

	List<int> get codeUnits => new CodeUnits(this);

	Runes get runes => new Runes(this);

	int indexOf(Pattern pattern, [int start = 0]) {
	checkNull(pattern);
	if (start is! int) throw argumentErrorValue(start);
	if (start < 0 \|\| start > this.length) {
	throw new RangeError.range(start, 0, this.length);
	}
	if (pattern is String) {
	return stringIndexOfStringUnchecked(this, pattern, start);
	}
	if (pattern is JSSyntaxRegExp) {
	JSSyntaxRegExp re = pattern;
	Match? match = firstMatchAfter(re, this, start);
	return (match == null) ? -1 : match.start;
	}
	for (int i = start; i <= this.length; i++) {
	if (pattern.matchAsPrefix(this, i) != null) return i;
	}
	return -1;
	}

	int lastIndexOf(Pattern pattern, [int? start]) {
	checkNull(pattern);
	if (start == null) {
	start = length;
	} else if (start is! int) {
	throw argumentErrorValue(start);
	} else if (start < 0 \|\| start > this.length) {
	throw new RangeError.range(start, 0, this.length);
	}
	if (pattern is String) {
	String other = pattern;
	if (start + other.length > this.length) {
	start = this.length - other.length;
	}
	return stringLastIndexOfUnchecked(this, other, start);
	}
	for (int i = start; i >= 0; i--) {
	if (pattern.matchAsPrefix(this, i) != null) return i;
	}
	return -1;
	}

	bool contains(Pattern other, [int startIndex = 0]) {
	checkNull(other);
	if (startIndex < 0 \|\| startIndex > this.length) {
	throw new RangeError.range(startIndex, 0, this.length);
	}
	return stringContainsUnchecked(this, other, startIndex);
	}

	bool get isEmpty => length == 0;

	bool get isNotEmpty => !isEmpty;

	int compareTo(String other) {
	if (other is! String) throw argumentErrorValue(other);
	return this == other
	? 0
	: JS('bool', r'# < #', this, other)
	? -1
	: 1;
	}

	// Note: if you change this, also change the function [S].
	String toString() => this;

	/// This is the [Jenkins hash function][1] but using masking to keep
	/// values in SMI range.
	///
	/// [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function
	int get hashCode {
	// TODO(ahe): This method shouldn't have to use JS. Update when our
	// optimizations are smarter.
	int hash = 0;
	for (int i = 0; i < length; i++) {
	hash = 0x1fffffff & (hash + JS<int>('int', r'#.charCodeAt(#)', this, i));
	hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
	hash = JS('int', '# ^ (# >> 6)', hash, hash);
	}
	hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
	hash = JS<int>('int', '# ^ (# >> 11)', hash, hash);
	return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
	}

	Type get runtimeType => String;

	int get length => JS('int', r'#.length', this);

	String operator [](int index) {
	if (index is! int) throw diagnoseIndexError(this, index);
	// This form of the range test correctly rejects NaN.
	if (!(index >= 0 && index < length)) throw diagnoseIndexError(this, index);
	return JS('String', '#[#]', this, index);
	}
	}