https://segmentfault.com/a/1190000012646488 https://yangbo5207.github.io/wutongluo/
说明:此处只是记录阅读前端基础进阶的理解和总结,如有需要请阅读上面的链接
1.如何让元素动起来
要让元素动起来就要修改元素的top、left 、translate 属性。因为使用top、left会使页面重绘,而translate不会,所以从性能上一般优先使用translate。另外因为translate是transform的一个用法,而transform是css3中的所以需要判断一下浏览器是否支持,不同的浏览器写法大概有几种
['transform', 'webkitTransform', 'MozTransform', 'msTransform', 'OTransform']
//判断当前浏览器支持哪种transformfunction getTransform() {var transform = '';var divStyle = document.createElement("div").style;//不同的浏览器大概支持如下几种transformvar transArray = ['transform', 'webkitTransform', 'MozTransform', 'msTransform', 'OTransform']for (var x in transArray) {if (transArray[x] in divStyle)return transform = transArray[x];}return transform;}
2.获取元素初始位置
//获取目标元素样式function getStyle(elem, property) {//ie 通过currentStyle获取样式,其他浏览器通过getComputedStyle,getComputedStyle是一个方法return document.defaultView.getComputedStyle ? document.defaultView.getComputedStyle(elem, false)[property] : elem.currentStyle[property];}//获取元素的初始位置function getTargetPos(elem) {var pos = { x: 0, y: 0 };var transform = getTransform();if (transform ) {var transformValue = getStyle(elem,transform);if (transformValue == 'none') {elem.style[transform] = 'translate(0, 0)';return pos;} else {console.log(transformValue);var temp = transformValue.match(/[0-9,\s\.]+/)[0].split(',');return pos = {x: parseInt(temp[4].trim()),y: parseInt(temp[5].trim())};}} else {if (getStyle(elem, 'position') == 'static') {elem.style.position = 'relative';return pos;} else {var x = parseInt(getStyle(elem, 'left') ? getStyle(elem, 'left') : 0);var y = parseInt(getStyle(elem, 'top') ? getStyle(elem, 'top') : 0);return pos = {x: x,y: y};}}}
设置元素位置
//设置元素位置function setTargetPos(elem, pos) {var transform = getTransform();if (transform != "") {elem.style[transform] = "translate(" + pos.x + "px," + pos.y + "px)";} else {elem.style.left = pos.x + "px";elem.style.top = pos.y + "px";}return elem;}
3.事件
拖拽的原理:mousedown记录元素和鼠标的初始位置,添加mousemove、mouseup事件,mousemove事件随着鼠标移动获取鼠标当前位置。移动后的鼠标位置-鼠标的初始位置=移动后的元素位置-元素的初始位置,如果用diss表示移动后的鼠标位置-鼠标的初始位置,那么元素移动后的位置=元素的初始位置+diss。这样在鼠标移动时就可以得到元素的位置。mouseup移除mousemove、mouseup事件和做其他处理
function start(event) {startX = event.pageX; //获取鼠标初始位置startY = event.pageY;var pos = getTargetPos(oElem);sourceX = pos.x;sourceY = pos.y;document.addEventListener('mousemove', move, false);document.addEventListener('mouseup', end, false);}function move(event) {var currentX = event.pageX;var currentY = event.pageY;var distanceX = currentX - startX;var distanceY = currentY - startY;setTargetPos(oElem, { x: (sourceX + distanceX).toFixed(), y: (sourceY + distanceY).toFixed() });}function end(event) {document.removeEventListener('mousemove', move);document.removeEventListener('mouseup', end);}
完整的js代码
var oElem = document.getElementById("div1"); //document.getElementById("div1")必须在元素加载完成后才能获取到元素,所以这个JavaScript必须放在body后,否则返回nullvar startX = 0;var startY = 0;var sourceX = 0;var sourceY = 0;oElem.addEventListener('mousedown', start, false);//获取目标元素样式function getStyle(elem, property) {//ie 通过currentStyle获取样式,其他浏览器通过getComputedStyle,getComputedStyle是一个方法return document.defaultView.getComputedStyle ? document.defaultView.getComputedStyle(elem, false)[property] : elem.currentStyle[property];}//判断当前浏览器支持哪种transformfunction getTransform() {var transform = '';var divStyle = document.createElement("div").style;//不同的浏览器大概支持如下几种transformvar transArray = ['transform', 'webkitTransform', 'MozTransform', 'msTransform', 'OTransform']for (var x in transArray) {if (transArray[x] in divStyle)return transform = transArray[x];}return transform;}//获取元素的初始位置function getTargetPos(elem) {var pos = { x: 0, y: 0 };var transform = getTransform();if (transform ) {var transformValue = getStyle(elem,transform);if (transformValue == 'none') {elem.style[transform] = 'translate(0, 0)';return pos;} else {var temp = transformValue.match(/[0-9,\s\.]+/)[0].split(',');return pos = {x: parseInt(temp[4].trim()),y: parseInt(temp[5].trim())};}} else {if (getStyle(elem, 'position') == 'static') {elem.style.position = 'relative';return pos;} else {var x = parseInt(getStyle(elem, 'left') ? getStyle(elem, 'left') : 0);var y = parseInt(getStyle(elem, 'top') ? getStyle(elem, 'top') : 0);return pos = {x: x,y: y};}}}//设置元素位置function setTargetPos(elem, pos) {var transform = getTransform();if (transform != "") {elem.style[transform] = "translate(" + pos.x + "px," + pos.y + "px)";} else {elem.style.left = pos.x + "px";elem.style.top = pos.y + "px";}return elem;}function start(event) {startX = event.pageX; //获取鼠标初始位置startY = event.pageY;var pos = getTargetPos(oElem);sourceX = pos.x;sourceY = pos.y;document.addEventListener('mousemove', move, false);document.addEventListener('mouseup', end, false);}function move(event) {var currentX = event.pageX;var currentY = event.pageY;var distanceX = currentX - startX;var distanceY = currentY - startY;setTargetPos(oElem, { x: (sourceX + distanceX).toFixed(), y: (sourceY + distanceY).toFixed() });}function end(event) {document.removeEventListener('mousemove', move);document.removeEventListener('mouseup', end);}
我们可以把以上代码封装到一个模块里面,使用的时候只要传元素Id就可以了。
;(function () {var transform = getTransform();//构造函数function Drag(selector) {this.elem = typeof selector == 'Object' ? selector : document.getElementById(selector);this.startX = 0;this.startY = 0;this.sourceX = 0;this.sourceY = 0;this.init();//初始化 }//原型Drag.prototype = {constructor: Drag,init: function () { this.setDrag(); },//获取目标元素样式getStyle: function (property) {//ie 通过currentStyle获取样式,其他浏览器通过getComputedStyle,getComputedStyle是一个方法return document.defaultView.getComputedStyle ? document.defaultView.getComputedStyle(this.elem, false)[property] : this.elem.currentStyle[property];},//获取元素的初始位置getTargetPos: function () {var pos = { x: 0, y: 0 };if (transform != "") {var transformValue = this.getStyle(transform);if (transformValue == 'none') {this.elem.style[transform] = 'translate(0, 0)';return pos;} else {var temp = transformValue.match(/[0-9,\s\.]+/)[0].split(',');return pos = {x: parseInt(temp[4].trim()),y: parseInt(temp[5].trim())};}} else {if (this.getStyle(this.elem, 'position') == 'static') {this.elem.style.position = 'relative';return pos;} else {var x = parseInt(this.getStyle('left') ? this.getStyle('left') : 0);var y = parseInt(this.getStyle('top') ? this.getStyle('top') : 0);return pos = {x: x,y: y};}}},//设置元素位置setTargetPos: function (pos) {if (transform != "") {this.elem.style[transform] = "translate(" + pos.x + "px," + pos.y + "px)";} else {this.elem.style.left = pos.x + "px";this.elem.style.top = pos.y + "px";}},setDrag: function () {var self = this;//因为绑定的方法是独立执行的,this指向并不是Drag对象,所以必须使用闭包this.elem.addEventListener('mousedown', start, false);function start(event) {self.startX = event.pageX; //获取鼠标初始位置self.startY = event.pageY;var pos = self.getTargetPos();self.sourceX = pos.x;self.sourceY = pos.y;document.addEventListener('mousemove', move, false);document.addEventListener('mouseup', end, false);}function move(event) {var currentX = event.pageX;var currentY = event.pageY;var distanceX = currentX - self.startX;var distanceY = currentY - self.startY;self.setTargetPos({ x: (self.sourceX + distanceX).toFixed(), y: (self.sourceY + distanceY).toFixed() });}function end(event) {document.removeEventListener('mousemove', move);document.removeEventListener('mouseup', end);}}}// 私有方法,仅仅用来获取transform的兼容写法function getTransform() {var transform = '',divStyle = document.createElement('div').style,transformArr = ['transform', 'webkitTransform', 'MozTransform', 'msTransform', 'OTransform'],i = 0,len = transformArr.length;for (; i < len; i++) {if (transformArr[i] in divStyle) {return transform = transformArr[i];}}return transform;}window .Drag=Drag;//对外暴露构造方法 })();new Drag('div1');//拖拽实例