Optimize tokenize()

- Wrap internal variables in a closure to prevent repeated instantiation when called.
- Define every internal function using a direct function expression rather than an anonymous function.

Author: danny0838

parse-css.js

@@ -78,45 +78,48 @@ function asciiCaselessMatch(s1, s2) {
   return s1.toLowerCase() == s2.toLowerCase();
 }
 
-function tokenize(str) {
-  str = preprocess(str);
-  var i = -1;
-  var tokens = [];
-  var code;
+var tokenize = (function () {
+  let str;
+  let i;
+  let tokens;
+  let code;
 
-  var codepoint = function(i) {
+  function codepoint(i) {
     if(i >= str.length) {
       return 0;
     }
     return str[i];
   }
-  var next = function(num) {
+  function next(num) {
     if(num === undefined)
       num = 1;
     if(num > 3)
       throw new SpecError("no more than three codepoints of lookahead.");
     return codepoint(i+num);
-  };
-  var consume = function(num) {
+  }
+  function consume(num) {
     if(num === undefined)
       num = 1;
     i += num;
     code = codepoint(i);
     //console.log('Consume '+i+' '+String.fromCharCode(code) + ' 0x' + code.toString(16));
     return true;
-  };
-  var reconsume = function() {
+  }
+  function reconsume() {
     i -= 1;
     return true;
-  };
-  var eof = function(codepoint) {
+  }
+  function eof(codepoint) {
     if(codepoint === undefined) codepoint = code;
     return codepoint == 0;
-  };
-  var donothing = function() {};
-  var parseerror = function() { console.log("Parse error at index " + i + ", processing codepoint 0x" + code.toString(16) + ".");return true; };
+  }
+  function donothing() {}
+  function parseerror() {
+    console.log("Parse error at index " + i + ", processing codepoint 0x" + code.toString(16) + ".");
+    return true;
+  }
 
-  var consumeAToken = function() {
+  function consumeAToken() {
     consumeComments();
     consume();
     if(whitespace(code)) {
@@ -206,9 +209,9 @@ function tokenize(str) {
     }
     else if(eof()) return new EOFToken();
     else return new DelimToken(code);
-  };
+  }
 
-  var consumeComments = function() {
+  function consumeComments() {
     while(next(1) == 0x2f && next(2) == 0x2a) {
       consume(2);
       while(true) {
@@ -222,9 +225,9 @@ function tokenize(str) {
         }
       }
     }
-  };
+  }
 
-  var consumeANumericToken = function() {
+  function consumeANumericToken() {
     var {value, isInteger, sign} = consumeANumber();
     if(wouldStartAnIdentifier(next(1), next(2), next(3))) {
       const unit = consumeAName();
@@ -235,9 +238,9 @@ function tokenize(str) {
     } else {
       return new NumberToken(value, isInteger, sign);
     }
-  };
+  }
 
-  var consumeAnIdentlikeToken = function() {
+  function consumeAnIdentlikeToken() {
     var str = consumeAName();
     if(str.toLowerCase() == "url" && next() == 0x28) {
       consume();
@@ -255,9 +258,9 @@ function tokenize(str) {
     } else {
       return new IdentToken(str);
     }
-  };
+  }
 
-  var consumeAStringToken = function(endingCodePoint) {
+  function consumeAStringToken(endingCodePoint) {
     if(endingCodePoint === undefined) endingCodePoint = code;
     var string = "";
     while(consume()) {
@@ -279,9 +282,9 @@ function tokenize(str) {
         string += String.fromCodePoint(code);
       }
     }
-  };
+  }
 
-  var consumeAURLToken = function() {
+  function consumeAURLToken() {
     var token = new URLToken("");
     while(whitespace(next())) consume();
     if(eof(next())) return token;
@@ -313,9 +316,9 @@ function tokenize(str) {
         token.value += String.fromCodePoint(code);
       }
     }
-  };
+  }
 
-  var consumeEscape = function() {
+  function consumeEscape() {
     // Assume the the current character is the \
     // and the next code point is not a newline.
     consume();
@@ -339,18 +342,18 @@ function tokenize(str) {
     } else {
       return code;
     }
-  };
+  }
 
-  var areAValidEscape = function(c1, c2) {
+  function areAValidEscape(c1, c2) {
     if(c1 != 0x5c) return false;
     if(newline(c2)) return false;
     return true;
-  };
-  var startsWithAValidEscape = function() {
+  }
+  function startsWithAValidEscape() {
     return areAValidEscape(code, next());
-  };
+  }
 
-  var wouldStartAnIdentifier = function(c1, c2, c3) {
+  function wouldStartAnIdentifier(c1, c2, c3) {
     if(c1 == 0x2d) {
       return namestartchar(c2) || c2 == 0x2d || areAValidEscape(c2, c3);
     } else if(namestartchar(c1)) {
@@ -360,12 +363,12 @@ function tokenize(str) {
     } else {
       return false;
     }
-  };
-  var startsWithAnIdentifier = function() {
+  }
+  function startsWithAnIdentifier() {
     return wouldStartAnIdentifier(code, next(1), next(2));
-  };
+  }
 
-  var wouldStartANumber = function(c1, c2, c3) {
+  function wouldStartANumber(c1, c2, c3) {
     if(c1 == 0x2b || c1 == 0x2d) {
       if(digit(c2)) return true;
       if(c2 == 0x2e && digit(c3)) return true;
@@ -378,12 +381,12 @@ function tokenize(str) {
     } else {
       return false;
     }
-  };
-  var startsWithANumber = function() {
+  }
+  function startsWithANumber() {
     return wouldStartANumber(code, next(1), next(2));
-  };
+  }
 
-  var consumeAName = function() {
+  function consumeAName() {
     var result = "";
     while(consume()) {
       if(namechar(code)) {
@@ -395,9 +398,9 @@ function tokenize(str) {
         return result;
       }
     }
-  };
+  }
 
-  var consumeANumber = function() {
+  function consumeANumber() {
     let isInteger = true;
     let sign;
     let numberPart = "";
@@ -443,9 +446,9 @@ function tokenize(str) {
     // if(exponentPart) value = value * Math.pow(10, +exponentPart);
 
     return {value, isInteger, sign};
-  };
+  }
 
-  var consumeTheRemnantsOfABadURL = function() {
+  function consumeTheRemnantsOfABadURL() {
     while(consume()) {
       if(code == 0x29 || eof()) {
         return;
@@ -456,22 +459,30 @@ function tokenize(str) {
         donothing();
       }
     }
-  };
+  }
 
 
+  function tokenize(input) {
+    str = preprocess(input);
+    i = -1;
+    tokens = [];
+    code;
 
-  var iterationCount = 0;
-  while (true) {
-    var token = consumeAToken();
-    tokens.push(token);
-    if (token instanceof EOFToken) {
-      break;
+    var iterationCount = 0;
+    while (true) {
+      var token = consumeAToken();
+      tokens.push(token);
+      if (token instanceof EOFToken) {
+        break;
+      }
+      iterationCount++;
+      if(iterationCount > str.length*2) throw new Error("I'm infinite-looping!");
     }
-    iterationCount++;
-    if(iterationCount > str.length*2) throw new Error("I'm infinite-looping!");
+    return tokens;
   }
-  return tokens;
-}
+
+  return tokenize;
+})();
 
 class CSSParserToken {
   constructor(type) {