html - How to set Id to button created using Javascript? -

// how set id created buttons?

for(i=1;i<=3;i++) {            var btn = document.createelement("button");// create       button using java script     btn.classname = "btnsize";      var txt = document.createtextnode(num++);//creat text on button     btn.appendchild(txt);//attached text on button     document.getelementbyid("xyz").appendchild(btn);//atache button text in div  }  

for (i = 1; <= 3; i++) {  var btn = document.createelement("button");  btn.setattribute("class","btnsize");  btn.setattribute("id","btnid"+i);  var txt = document.createtextnode("button");  btn.appendchild(txt);  document.getelementbyid("xyz").appendchild(btn);  }