我有一个短代码[gf_popup pause="1000" location="bottom"] 位置属性一直返回为Uncaught ReferenceError: bottom is not defined. 想知道为什么吗？以下是代码的主要部分：

function gfpu_shortcode($atts = [], $content = null, $tags = \'\')
{

    // normalize attribute keys, lowercase
$atts = array_change_key_case((array)$atts, CASE_LOWER);

// override default attributes with user attributes
$gfpu_atts = shortcode_atts([
                                 \'pause\'    => 5000,
                                 \'location\' => \'false\',
                                 \'popTrigger\'   => \'false\',
                             ], $atts, $tag);

    $timer = esc_html__($gfpu_atts[\'pause\'], \'gf_popup\');
    $location = esc_html__($gfpu_atts[\'location\'], \'gf_popup\');
    $popTrigger = esc_html__($gfpu_atts[\'popTrigger\'], \'gf_popup\'); 

}
add_shortcode(\'gf_popup\', \'gfpu_shortcode\');