If you use a let within the init-form of an outer let, the result is invalid javascript code.

Here is a simplified example:

(ps (let ((x (let ((y (a))) 
       (b) 
               y)))
      (1+ x)))

==>

"(function () {
    var y;
    var x = (y = a(), (b(), y));
    return x + 1;
})();"

Not that I would normally write such code, but the inner "let" was generated by a macro.
And many macros use "let" with gensyms.  In my case, the macro used "ps-once-only".

Andy Peterson