If you want to write some code, you can use a shortcode:

add_shortcode( 'unescape_js', 'add_js_code' );

function add_js_code( $atts, $contents="" )
{
    $contents = html_entity_decode( $content );
    return $contents;
}

Usage – in text editor

[unescape_js] Your js code && more js codes…[/unescape_js]

But saving js code directly into DB is not recommended at all.