JSFiddle - React, Tailwind, and code Playground

HTML

<div id="copyAll">click to copyAll</div>
<div id="copyProps">click to copyProps</div>

JavaScript

document.getElementById('copyAll').onclick = function(e) {

  e = e || event
  var d = new Date()
  for(var i =0; i<1000;i++) {
    var o = {}
    for(var p in e) {
     o[p] = e[p]
    }
  }
  alert(new Date()-d)    

}

var props = "altKey attrChange attrName bubbles button cancelable charCode clientX clientY ctrlKey currentTarget data detail eventPhase fromElement handler keyCode layerX layerY metaKey newValue offsetX offsetY pageX pageY prevValue relatedNode relatedTarget screenX screenY shiftKey srcElement target toElement view wheelDelta which".split(" ")

document.getElementById('copyProps').onclick = function(e) {

  e = e || event
  var d = new Date()
  for(var i =0; i<1000;i++) {
    var o = {}
    var len = props.length
    for(var j=0;j<len;j++) {
     var p = props[j]
     o[p] = e[p]
    }
  }
  alert(new Date()-d)    

}