Converting native javascript to jquery

Converting native javascript to jquery

Hello

I need some help converting this to jquery javascript

function center() {
 
   var rcontent = document.getElementById("left").getElementsByTagName("*").length;
     
   if (document.getElementById("left").getElementsByTagName('img')[0]) {
      var imgtag = document.getElementById("left").getElementsByTagName('img')[0].src;
      if (imgtag.indexOf("test") > 1 && imgtag.indexOf("trans.gif") > 1) {
         document.getElementById("outer").style.width='1400px' 
          }
      else if (imgtag.indexOf("trans.gif") > 1 ) {
          document.getElementById("outer").style.width='1400px'  }
      else if (imgtag.indexOf("test") > 1) {
          document.getElementById("outer").style.width='1400px'   }
        }
    
    else if (rcontent >= 1)    {}
}















Especially this part

var imgtag = document.getElementById("left").getElementsByTagName('img')[0].src;

  if (imgtag.indexOf("test") > 1 && imgtag.indexOf("trans.gif") > 1) {
         document.getElementById("outer").style.width='1400px' 
     }