Why `add_to_foot()` doesnt work with `cp_js_end` hook?

Question

i use cp_js_end for use javascript in control panel pages, and add_to_foo() for add js files,

but that doesnt work! i test it in construct & hook functions but that doesnt work, code:

function cp_js_end() {
ee()->cp->add_to_foot('< script src="http://localhost/main.js"></ script>');

$output = $this->EE->extension->last_call;
$output .= 'console.log("Script included")';
return $output; }

and i cant see “Script included” in console and there is no included file!

thanks for help :)