java - How to replace a value of an attribute in JS function on run time? -

i working on java application (besides other things) produces html. in html need change value of 1 attribute inside 1 js function every time run it. process this:

1. every time run html, application connect mysql database , retrieves needed values. 2. values parsed html , replacing keywords set purpose of replacing. 

i have done replacing text defining keyword datatext in html

<p>datatext</p> 

and in java application, made replacing this:

public void visitstringnode (text string)         {           ...              else if (string.gettext().equals("datatext")){                   string.settext(text);             }         } 

where text string retrieved database. wanted same replacing value of 1 attribute within js function setting keyword datavideo :

function replacesrcc() {      var elem = document.getelementsbytagname("embed")[0];         copy = elem.clonenode();     copy.src = datavideo;     elem.parentnode.replacechild(copy, elem);     }  

and in java make replacing in previous case:

else if (string.gettext().equals("datavideo")){                       string.settext(video_link);                 } 

where video_link string containing youtube link retrieved database. this, however, not work. debugging says fails search datavideo keyworkd within html. suggestions?

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edit : function replacesrcc() called on page load, this:

<script> function replacesrcc() {      var elem = document.getelementsbytagname("embed")[0];         copy = elem.clonenode();     copy.src = "https://www.youtube.com/v/skqennnt_vg?version=3";     elem.parentnode.replacechild(copy, elem);     }        if (window.addeventlistener){          window.addeventlistener('load', replacesrcc, false);     } else if (window.attachevent) {         window.attachevent('onload', replacesrcc);     }  </script>