pure javascript draggable element

Question

I know there\'re example of doing this on the web but every example is different and so is my own implementation. I\'m trying to figure what\'s wrong with my implementation

Answer 1

Quite interesting, had so far only done it with jQuery. Rewrote it a bit and made sure that every mousemove has it's event listener removed afterwards - that would be a memory leak that you might start to notice otherwise :

http://jsfiddle.net/8wtq17L8/

var contextmenu = document.getElementById('contextMenu');
var initX, initY, mousePressX, mousePressY;

contextmenu.addEventListener('mousedown', function(event) {

    initX = this.offsetLeft;
    initY = this.offsetTop;
    mousePressX = event.clientX;
    mousePressY = event.clientY;

    this.addEventListener('mousemove', repositionElement, false);

    window.addEventListener('mouseup', function() {
      contextmenu.removeEventListener('mousemove', repositionElement, false);
    }, false);

}, false);

function repositionElement(event) {
    this.style.left = initX + event.clientX - mousePressX + 'px';
    this.style.top = initY + event.clientY - mousePressY + 'px';
}

Seems to be working well. :-)

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Edit - thought I'd add a version with touch support too (although newer devices seem to emulate mouse events). Not like Jquery where you can select multiple event listeners so it's mostly a repetition, just with touch events :

http://codepen.io/Shikkediel/pen/VLZKor?editors=011

var object = document.getElementById('element'),
initX, initY, firstX, firstY;

object.addEventListener('mousedown', function(e) {

    e.preventDefault();
    initX = this.offsetLeft;
    initY = this.offsetTop;
    firstX = e.pageX;
    firstY = e.pageY;

    this.addEventListener('mousemove', dragIt, false);

    window.addEventListener('mouseup', function() {
        object.removeEventListener('mousemove', dragIt, false);
    }, false);

}, false);

object.addEventListener('touchstart', function(e) {

    e.preventDefault();
    initX = this.offsetLeft;
    initY = this.offsetTop;
    var touch = e.touches;
    firstX = touch[0].pageX;
    firstY = touch[0].pageY;

    this.addEventListener('touchmove', swipeIt, false);

    window.addEventListener('touchend', function(e) {
        e.preventDefault();
        object.removeEventListener('touchmove', swipeIt, false);
    }, false);

}, false);

function dragIt(e) {
    this.style.left = initX+e.pageX-firstX + 'px';
    this.style.top = initY+e.pageY-firstY + 'px';
}

function swipeIt(e) {
    var contact = e.touches;
    this.style.left = initX+contact[0].pageX-firstX + 'px';
    this.style.top = initY+contact[0].pageY-firstY + 'px';
}