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copied!<p>I guess you're using <a href="http://www.antlr.org/grammar/1206736738015/JavaScript.g" rel="nofollow noreferrer">this grammar</a>.</p> <p>Although that grammar suggests a proper AST is created, this is not the case. It uses some inline operators to exclude certain tokens from the parse-tree, but it never creates any roots for the tree, resulting in a completely flat parse tree. From this, you can't get all global vars in a reasonable way.</p> <p>You'll need to adjust the grammar slightly:</p> <p>Add the following under the <code>options { ... }</code> at the top of the grammar file:</p> <pre><code>tokens { VARIABLE; FUNCTION; } </code></pre> <p>Now replace the following rules: <code>functionDeclaration</code>, <code>functionExpression</code> and <code>variableDeclaration</code> with these:</p> <pre><code>functionDeclaration : 'function' LT* Identifier LT* formalParameterList LT* functionBody -> ^(FUNCTION Identifier formalParameterList functionBody) ; functionExpression : 'function' LT* Identifier? LT* formalParameterList LT* functionBody -> ^(FUNCTION Identifier? formalParameterList functionBody) ; variableDeclaration : Identifier LT* initialiser? -> ^(VARIABLE Identifier initialiser?) ; </code></pre> <p>Now a more suitable tree is generated. If you now parse the source:</p> <pre><code>var a = 1; function foo() { var b = 2; } var c = 3; </code></pre> <p>the following tree is generated:</p> <p><img src="https://i.stack.imgur.com/Opfe5.png" alt="alt text"></p> <p>All you now have to do is iterate over the children of the root of your tree and when you stumble upon a <code>VARIABLE</code> token, you know it's a "global" since all other variables will be under <code>FUNCTION</code> nodes.</p> <p>Here's how to do that:</p> <pre><code>import org.antlr.runtime.*; import org.antlr.runtime.tree.*; public class Main { public static void main(String[] args) throws Exception { String source = "var a = 1; function foo() { var b = 2; } var c = 3;"; ANTLRStringStream in = new ANTLRStringStream(source); JavaScriptLexer lexer = new JavaScriptLexer(in); CommonTokenStream tokens = new CommonTokenStream(lexer); JavaScriptParser parser = new JavaScriptParser(tokens); JavaScriptParser.program_return returnValue = parser.program(); CommonTree tree = (CommonTree)returnValue.getTree(); for(Object o : tree.getChildren()) { CommonTree child = (CommonTree)o; if(child.getType() == JavaScriptParser.VARIABLE) { System.out.println("Found a global var: "+child.getChild(0)); } } } } </code></pre> <p>which produces the following output:</p> <pre><code>Found a global var: a Found a global var: c </code></pre>

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