how to hide a button in javascript code example

Example 1: js hide div

//If you have jquery, you can use the following method:
$("#mydiv").hide(); //hides div.
$("#mydiv").show(); //shows div.
//If you don't have jquery...
//search up the following: html how to add jquery

Example 2: javascript hide a div

<div id="main"> 
  <p> Hide/show this div </p>
</div>

('#main').hide(); //to hide

// 2nd way, by injecting css using jquery
$("#main").css("display", "none");