=proto
int duk_is_null_or_undefined(duk_context *ctx, int index);

=stack
[ ... val! ... ]

=summary
<p>Returns 1 if value at <code>index</code> is either <code>null</code> or <code>undefined</code>,
otherwise returns 0.  If <code>index</code> is invalid, also returns 0.</p>

<p>This API call is similar to a <code>(x == null)</code> comparison in Ecmascript, which
is true for both <code>null</code> and <code>undefined</code>.</p>

=example
if (duk_is_null_or_undefined(ctx, -3)) {
    /* ... */
}

=tags
stack