Nathan University Lesson 2.2

gistfile1.js

var reverse = function(expr) {
    var make_node = function(t, left, right) {
        return {tag: t,
                left: left,
                right: right};
    };
    if (expr.tag == 'note') {
        return expr;
    }
    return make_node(expr.tag,
                     reverse(expr.right),
                     reverse(expr.left));
};

var endTime = function (time, expr) {
    if (expr.tag == 'note') {
        return time + expr.dur;
    }
    return endTime(time, expr.left) + endTime(time, expr.right);
};

var compile = function (musexpr) {
    
    if (musexpr.tag == 'note') {
        return [musexpr];
    }
    return compile(musexpr.left).concat(compile(musexpr.right));
};

I inlined make_node, IIRC.