js+drag实现拖动排序

这次来做一个拖动排序，带有动画效果，先上效果图:

每个li既是可拖动，同时也是容器，拖动到li上面时移动拖动的li。

先把html写好

<ul id="container">
        <li class="ele" draggable="true">1</li>
        <li class="ele" draggable="true">2</li>
        <li class="ele" draggable="true">3</li>
        <li class="ele" draggable="true">4</li>
</ul>

css

ul {
        list-style: none;
        margin: 200px;
    }

    .ele {
        width: 100%;
        height: 40px;
        border: 1px solid #999;
        background: #EA6E59;
        margin-top: 2px;
        border-radius: 10px;
        padding-left: 10px;
        color: white;
        cursor: move;
    }

js

var node = document.querySelector("#container");
var draging = null;
//使用事件委托，将li的事件委托给ul
node.ondragstart = function(event) {
        //console.log("start");
            //firefox设置了setData后元素才能拖动！！！！
        event.dataTransfer.setData("te", event.target.innerText); //不能使用text，firefox会打开新tab
        //event.dataTransfer.setData("self", event.target);
        draging = event.target;
    }
node.ondragover = function(event) {
        //console.log("onDrop over");
        event.preventDefault();
        var target = event.target;
            //因为dragover会发生在ul上，所以要判断是不是li
        if (target.nodeName === "LI") {
            if (target !== draging) {
                var targetRect = target.getBoundingClientRect();
                var dragingRect = draging.getBoundingClientRect();
                if (target) {
                    if (target.animated) {
                        return;
                    }
                }
                if (_index(draging) < _index(target)) {
                    target.parentNode.insertBefore(draging, target.nextSibling);
                } else {
                    target.parentNode.insertBefore(draging, target);
                }
                _animate(dragingRect, draging);
                _animate(targetRect, target);
            }
        }
    }
    //获取元素在父元素中的index
  function _index(el) {
        var index = 0;

        if (!el || !el.parentNode) {
            return -1;
        }

        while (el && (el = el.previousElementSibling)) {
            //console.log(el);
            index++;
        }

        return index;
    }

function _animate(prevRect, target) {
        var ms = 300;

        if (ms) {
            var currentRect = target.getBoundingClientRect();

            if (prevRect.nodeType === 1) {
                prevRect = prevRect.getBoundingClientRect();
            }

            _css(target, 'transition', 'none');
            _css(target, 'transform', 'translate3d(' +
                (prevRect.left - currentRect.left) + 'px,' +
                (prevRect.top - currentRect.top) + 'px,0)'
            );

            target.offsetWidth; // 触发重绘
            //放在timeout里面也可以
            // setTimeout(function() {
            //     _css(target, 'transition', 'all ' + ms + 'ms');
            //     _css(target, 'transform', 'translate3d(0,0,0)');
            // }, 0);
            _css(target, 'transition', 'all ' + ms + 'ms');
            _css(target, 'transform', 'translate3d(0,0,0)');

            clearTimeout(target.animated);
            target.animated = setTimeout(function() {
                _css(target, 'transition', '');
                _css(target, 'transform', '');
                target.animated = false;
            }, ms);
        }
    }
    //给元素添加style
  function _css(el, prop, val) {
        var style = el && el.style;

        if (style) {
            if (val === void 0) {
                if (document.defaultView && document.defaultView.getComputedStyle) {
                    val = document.defaultView.getComputedStyle(el, '');
                } else if (el.currentStyle) {
                    val = el.currentStyle;
                }

                return prop === void 0 ? val : val[prop];
            } else {
                if (!(prop in style)) {
                    prop = '-webkit-' + prop;
                }

                style[prop] = val + (typeof val === 'string' ? '' : 'px');
            }
        }
    }