text: const UglifyJS = require('uglify-js')
  
  var code = function toplevel() {
    var a = foo("x", "y", (function(){
        var b = "stuff";
        var c = "bar";
    })(), 1, "z");
  };
  code = code.toString();
  console.log(code)
  var toplevel = UglifyJS.parse(code);
  var call_expression = null;
  var walker = new UglifyJS.TreeWalker(function(node, descend){
    if (node instanceof UglifyJS.AST_Call) {
        var tmp = call_expression;
        call_expression = node;
        descend();
        call_expression = tmp;
        return true; // prevent descending again
    }
    if (node instanceof UglifyJS.AST_Lambda) { // ← here
        // when encounters a lambda, temporarily forget
        // the call expression.
        var tmp = call_expression;
        call_expression = null;
        descend();
        call_expression = tmp;
        return true; // again, to prevent diving this node twice
    }
    if (node instanceof UglifyJS.AST_String && call_expression) {
        console.log("Found string: %s at %d,%d", node.getValue(),
                    node.start.line, node.start.col);
    }
  });
  toplevel.walk(walker);