make html element, dragable.

dragable.js

// dragableElement(document.querySelector("#mydiv"))

function dragableElement(a) {
	let f = 0,
		g = 0,
		d = 0,
		e = 0
	eh = a.querySelector("#header") || a
	eh.onmousedown = function(b) {
		b = b || window.event
		b.preventDefault()
		d = b.clientX
		e = b.clientY
		document.onmouseup = function() {
			document.onmousemove = null
		}
		document.onmousemove = function(c) {
			c.preventDefault()
			f = d - c.clientX
			g = e - c.clientY
			d = c.clientX
			e = c.clientY
			a.style.top = a.offsetTop - g + "px"
			a.style.left = a.offsetLeft - f + "px"
		}
	}
}