Changing button text onclick

Question

When I click on myButton1 button, I want the value to change to Close Curtain from Open Curtain.
HTML:

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Answer 1

var count=0;
document.getElementById("play").onclick = function(){


if(count%2 =="1"){

                document.getElementById("video").pause();
                document.getElementById("play").innerHTML ="Pause";
            }else {

            document.getElementById("video").play();
            document.getElementById("play").innerHTML ="Play";

            }
            ++count;