Convert HTML Script to Shortcode

I want to convert this code into a shortcode from the Code Snippets plugin, I have seen an example come up but when I put it it does not work, the example is the following:

add_shortcode( 'shortcode_name', function () {      $  out = '<p>write your HTML shortcode content here</p>';      return $  out; } ); 

I want to convert the following code to rotate banners:

<script>       rnd.today=new Date();     rnd.seed=rnd.today.getTime();      function rnd() {         rnd.seed = (rnd.seed*9301+49297) % 233280;         return rnd.seed/(233280.0);     }      function rand(number) {         var result = Math.floor(rnd() * number);         if (!result) result = 0;         return result     }     var bannerimgs = new Array("a.jpg", "b.jpg");     var bannerlnks = new Array("a.com", "b.com");     var banneralt = new Array("a", "b");     var rotatorHtml = "";     var endJs = "";      for(var img in bannerimgs){         var thisImg = new Image();         thisImg.src = bannerimgs[img];     }     var bannerimgCt = 2;     var bannercurrentAd = rand(bannerimgCt);     var openlink = "";     var bannerbanner = document.getElementById('banner');     var bannerlink = document.getElementById('banneradLink');              if(bannerlnks[bannercurrentAd] != ""){         rotatorHtml += '<a href="' + bannerlnks[bannercurrentAd] + '" id="banneradLink"  target="_blank">';         endJs = "</a>";     }     rotatorHtml += '<img src="' + bannerimgs[bannercurrentAd] + '" alt = "' + banneralt[bannercurrentAd] + '" id="bannerbanner">' + endJs;     document.getElementById("banner_div").innerHTML = rotatorHtml;   </script> 

How can this script be converted to a shortcode? I have replaced what it says but errors appear, then I do something wrong. How can this script be converted to a shortcode? Do you know any other way?