private void parseExpression() {
// Parse the expression until we encounter a comma or a semi-colon
// in the same brace nesting, bracket nesting（方括号嵌套） and paren nesting.
// Parse functions if any...
String symbol;
JavaScriptToken token;
ScriptOrFnScope currentScope;
JavaScriptIdentifier identifier;
int expressionBraceNesting = braceNesting; // 花括号嵌套
int bracketNesting = 0; // 方括号嵌套
int parensNesting = 0; //
int length = tokens.size();
while (offset < length) {
token = consumeToken();
currentScope = getCurrentScope(); // return scopes.peek();
switch (token.getType()) {
case Token.SEMI:
case Token.COMMA:
if (braceNesting == expressionBraceNesting && bracketNesting == 0 && parensNesting == 0) {
return;
}
break;
case Token.FUNCTION:
parseFunctionDeclaration();
break;
case Token.LC:
braceNesting++;
break;
case Token.RC:
braceNesting--;
assert braceNesting >= expressionBraceNesting;
break;
case Token.LB:
bracketNesting++;
break;
case Token.RB:
bracketNesting--;
break;
case Token.LP:
parensNesting++;
break;
case Token.RP:
parensNesting--;
break;
case Token.CONDCOMMENT:
if (mode == BUILDING_SYMBOL_TREE) {
protectScopeFromObfuscation(currentScope);
warn("不推荐使用JScript条件注释。" + (munge ? "使用JScript条件注释会降低压缩水平！" : ""), true);
}
break;
case Token.NAME:
symbol = token.getValue();
if (mode == BUILDING_SYMBOL_TREE) {
if (symbol.equals("eval")) {
protectScopeFromObfuscation(currentScope);
warn("不推荐使用'eval'关键字。" + (munge ? "使用'eval'会降低压缩水平！" : ""), true);
}
} else if (mode == CHECKING_SYMBOL_TREE) {
if ((offset < 2
|| (getToken(-2).getType() != Token.DOT
&& getToken(-2).getType() != Token.GET
&& getToken(-2).getType() != Token.SET))
&& getToken(0).getType() != Token.OBJECTLIT) {
identifier = getIdentifier(symbol, currentScope);
if (identifier == null) {
if (symbol.length() <= 3 && !builtin.contains(symbol)) {
// Here, we found an undeclared and
// un-namespaced symbol that is
// 3 characters or less in length. Declare it in
// the global scope.
// We don't need to declare longer symbols since
// they won't cause
// any conflict with other munged symbols.
globalScope.declareIdentifier(symbol, false);
// I removed the warning since was only being
// done when
// for identifiers 3 chars or less, and was just
// causing
// noise for people who happen to rely on an
// externally
// declared variable that happen to be that
// short. We either
// should always warn or never warn -- the fact
// that we
// declare the short symbols in the global space
// doesn't
// change anything.
// warn("Found an undeclared symbol: " + symbol,
// true);
}
} else {
identifier.incrementRefcount();
}
}
}
break;
}
}
}
private void parseScope(ScriptOrFnScope scope) {
String symbol;
JavaScriptToken token;
JavaScriptIdentifier identifier;
int length = tokens.size();
enterScope(scope); // 进入范围(将scope压入栈scopes中)
while (offset < length) { // 在此函数调用前已设置为0
token = consumeToken(); // 消费tokens,offset自增
switch (token.getType()) {
case Token.VAR: // 注意后面没有break;
if (mode == BUILDING_SYMBOL_TREE) {
scope.incrementVarCount(); // 当前范围内的var数量加1
}
/* FALLSTHROUGH(falls through) 失败 */
case Token.CONST:
// The var keyword is followed by at least one symbol name.
// If several symbols follow, they are comma(逗号) separated.
for (; ; ) {
token = consumeToken();
assert token.getType() == Token.NAME;
// 判断关键字var、const后的变量是否已经定义，未定义则定义，已定义则输出警告
if (mode == BUILDING_SYMBOL_TREE) {
symbol = token.getValue();
if (scope.getIdentifier(symbol) == null) {
scope.declareIdentifier(symbol, true); // 声明标识符
} else {
warn("变量" + symbol + "已经在相同的作用域中声明", true);
}
}
token = getToken(0); // offset不自增,token.getValue()的值一般为'='或';'
assert token.getType() == Token.SEMI
|| token.getType() == Token.ASSIGN
|| token.getType() == Token.COMMA
|| token.getType() == Token.IN;
if (token.getType() == Token.IN) {
break;
} else {
parseExpression(); // 解释表达式（例如解释var a = 'u';或var a;）
token = getToken(-1); // 得到的是';'
if (token.getType() == Token.SEMI) { // 变量声明完成
break;
}
}
}
break;
case Token.FUNCTION:
parseFunctionDeclaration();
break;
case Token.LC:
braceNesting++;
break;
case Token.RC:
braceNesting--;
assert braceNesting >= scope.getBraceNesting();
if (braceNesting == scope.getBraceNesting()) { // 说明要离开当前作用域了
leaveCurrentScope(); // 离开当前作用域
return;
}
break;
case Token.WITH:
if (mode == BUILDING_SYMBOL_TREE) {
// Inside a 'with' block, it is impossible to figure out
// statically whether a symbol is a local variable or an
// object member. As a consequence, the only thing we can
// do is turn the obfuscation off for the highest scope
// containing the 'with' block.
protectScopeFromObfuscation(scope);
warn("不推荐使用with关键字。" + (munge ? " 使用with会降低压缩水平" : ""), true);
}
break;
case Token.CATCH:
parseCatch();
break;
case Token.CONDCOMMENT:
if (mode == BUILDING_SYMBOL_TREE) {
protectScopeFromObfuscation(scope);
warn("不推荐使用JScript条件注释。" + (munge ? "使用JScript条件解释会降低压缩水平。" : ""), true);
}
break;
case Token.NAME:
symbol = token.getValue();
if (mode == BUILDING_SYMBOL_TREE) {
if (symbol.equals("eval")) {
protectScopeFromObfuscation(scope);
warn("不推荐使用'eval'关键字。" + (munge ? "使用'eval'会降低压缩水平！" : ""), true);
}
} else if (mode == CHECKING_SYMBOL_TREE) {
if ((offset < 2 || getToken(-2).getType() != Token.DOT)
&& getToken(0).getType() != Token.OBJECTLIT) {
identifier = getIdentifier(symbol, scope);
if (identifier == null) {
if (symbol.length() <= 3 && !builtin.contains(symbol)) {
// Here, we found an undeclared and
// un-namespaced symbol that is
// 3 characters or less in length. Declare it in
// the global scope.
// We don't need to declare longer symbols since
// they won't cause
// any conflict with other munged symbols.
globalScope.declareIdentifier(symbol, false);
// warn("Found an undeclared symbol: " + symbol,
// true);
}
} else {
identifier.incrementRefcount();
}
}
}
break;
}
}
}
private static boolean isValidIdentifier(String s) {
Matcher m = SIMPLE_IDENTIFIER_NAME_PATTERN.matcher(s);
return (m.matches() && !reserved.contains(s));
}