andrey3681,
так?
<script>
function test(){
var el = document.getElementById("btn");
el.onclick = function(){
if (el.innerHTML == "Play"){
el.innerHTML = "Pause";
//document.getElementById(\'player\').play()
}else{
el.innerHTML = "Play";
//document.getElementById(\'player\').pause()
}
}
}
</script>
<body onload = "test()">
<button id = "btn">Play</button>