JS - 如何在特定页面上执行代码

I would like to execute this js code only at page: "header-26.php" using js only.

if (document.createElement &&
(meta = document.createElement('meta'))) {
meta.name = "xxx";
meta.content = "xxx";
document.getElementsByTagName('head').item(0).appendChild(meta);
}

How can I do that?

Thank you very much in advance.

In header-26.php

echo the javascript code:

echo '<script>
      if (document.createElement &&
         (meta = document.createElement('meta'))) {
         meta.name = "xxx";
         meta.content = "xxx";
         document.getElementsByTagName('head').item(0).appendChild(meta);
       }
      </script>';

 if (window.location.pathname == 'header-26.php') {
  if (document.createElement &&
  (meta = document.createElement('meta'))) {
  meta.name = "xxx";
  meta.content = "xxx";
  document.getElementsByTagName('head').item(0).appendChild(meta);
  }
 }