SOURCE

function Elem (id) {
	this.elem = document.getElementById(id);
}
Elem.prototype.html = function (value) {
	let elem = this.elem;
	if (value) {
		elem.innerHTML = value;
		return this;
	} else {
		return elem.innerHTML;
	}
}
Elem.prototype.on = function (type, fn) {
	let elem = this.elem;
	elem.addEventListener(type,fn)
	return this
}

var div1 = new Elem('detail')
console.log(div1.html())
div1.html('<p>hello world</p>').on('click', function() {
	alert('hello');
})

<div id="detail">detail content <div>test inner div</div></div>