document.createTextNode

unobtrusive

HTML

<button onclick="addTextNode(this)">YES!</button>
<button>NO!</button>
<button>WE CAN!</button>
<hr />
<p id="p1">First line of paragraph.</p>

JavaScript

function addTextNode(evt) {
    var newtext = document.createTextNode(this.innerHTML),
        p1 = document.getElementById("p1");
    
    p1.appendChild(newtext);
}

function deneme(){
	console.log('deneme calisti');
}

var btns = document.getElementsByTagName("button");

for(i = 0; i < btns.length; i++){
    var button = btns[i]; 
    button.addEventListener("click", deneme());
}