let element = document.querySelector('#app') 
let s = ''
for (var key in element) {
  s += key + ',' 
}
console.log(s)

// 打印结果 align,title,lang,translate,dir,hidden,accessKey,draggable,spellcheck,aut ocapitalize,contentEditable,isContentEditable,inputMode,offsetParent,off setTop,offsetLeft,offsetWidth,offsetHeight,style,innerText,outerText,onc opy,oncut,onpaste,onabort,onblur,oncancel,oncanplay,oncanplaythrough,onc hange,onclick,onclose,oncontextmenu,oncuechange,ondblclick,ondrag,ondrag end,ondragenter,ondragleave,ondragover,ondragstart,ondrop,ondurationchan ge,onemptied,onended,onerror,onfocus,oninput,oninvalid,onkeydown,onkeypr ess,onkeyup,onload,onloadeddata,onloadedmetadata,onloadstart,onmousedown ,onmouseenter,onmouseleave,onmousemove,onmouseout,onmouseover,onmouseup, onmousewheel,onpause,onplay,onplaying,onprogress,onratechange,onreset,on resize,onscroll,onseeked,onseeking,onselect,onstalled,onsubmit,onsuspend ,ontimeupdate,ontoggle,onvolumechange,onwaiting,onwheel,onauxclick,ongot pointercapture,onlostpointercapture,onpointerdown,onpointermove,onpointe rup,onpointercancel,onpointerover,onpointerout,onpointerenter,onpointerl eave,onselectstart,onselectionchange,onanimationend,onanimationiteration ,onanimationstart,ontransitionend,dataset,nonce,autofocus,tabIndex,click ,focus,blur,enterKeyHint,onformdata,onpointerrawupdate,attachInternals,n amespaceURI,prefix,localName,tagName,id,className,classList,slot,part,at tributes,shadowRoot,assignedSlot,innerHTML,outerHTML,scrollTop,scrollLef t,scrollWidth,scrollHeight,clientTop,clientLeft,clientWidth,clientHeight ,attributeStyleMap,onbeforecopy,onbeforecut,onbeforepaste,onsearch,eleme ntTiming,previousElementSibling,nextElementSibling,children,firstElement Child,lastElementChild,childElementCount,onfullscreenchange,onfullscreen error,onwebkitfullscreenchange,onwebkitfullscreenerror,setPointerCapture ,releasePointerCapture,hasPointerCapture,hasAttributes,getAttributeNames ,getAttribute,getAttributeNS,setAttribute,setAttributeNS,removeAttribute ,removeAttributeNS,hasAttribute,hasAttributeNS,toggleAttribute,getAttrib uteNode,getAttributeNodeNS,setAttributeNode,setAttributeNodeNS,removeAtt ributeNode,closest,matches,webkitMatchesSelector,attachShadow,getElement sByTagName,getElementsByTagNameNS,getElementsByClassName,insertAdjacentE lement,insertAdjacentText,insertAdjacentHTML,requestPointerLock,getClien tRects,getBoundingClientRect,scrollIntoView,scroll,scrollTo,scrollBy,scr ollIntoViewIfNeeded,animate,computedStyleMap,before,after,replaceWith,re move,prepend,append,querySelector,querySelectorAll,requestFullscreen,web kitRequestFullScreen,webkitRequestFullscreen,createShadowRoot,getDestina tionInsertionPoints,ELEMENT_NODE,ATTRIBUTE_NODE,TEXT_NODE,CDATA_SECTION_ NODE,ENTITY_REFERENCE_NODE,ENTITY_NODE,PROCESSING_INSTRUCTION_NODE,COMME NT_NODE,DOCUMENT_NODE,DOCUMENT_TYPE_NODE,DOCUMENT_FRAGMENT_NODE,NOTATION _NODE,DOCUMENT_POSITION_DISCONNECTED,DOCUMENT_POSITION_PRECEDING,DOCUMEN T_POSITION_FOLLOWING,DOCUMENT_POSITION_CONTAINS,DOCUMENT_POSITION_CONTAI NED_BY,DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC,nodeType,nodeName,baseU RI,isConnected,ownerDocument,parentNode,parentElement,childNodes,firstCh ild,lastChild,previousSibling,nextSibling,nodeValue,textContent,hasChild Nodes,getRootNode,normalize,cloneNode,isEqualNode,isSameNode,compareDocu mentPosition,contains,lookupPrefix,lookupNamespaceURI,isDefaultNamespace ,insertBefore,appendChild,replaceChild,removeChild,addEventListener,remo veEventListener,dispatchEvent