JS面向物件程式設計實現的拖拽功能案例詳解
阿新 • • 發佈:2020-03-04
本文例項講述了JS面向物件程式設計實現的拖拽功能。分享給大家供大家參考,具體如下:
原始的面向過程程式碼:
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <style> #box { width: 100px; height: 100px; background: blue; position: absolute; } </style> <title>拖拽</title> <script> var oBox=null; var disX=0; var disY=0; window.onload=function(){ oBox=document.getElementById('box'); oBox.onmousedown=fnDown; }; //滑鼠按下事件 function fnDown(ev){ var oEvent = ev||event; disX = oEvent.clientX - oBox.offsetLeft; disY = oEvent.clientY - oBox.offsetTop; document.onmousemove = fnMove; document.onmouseup = fnUp; } //滑鼠移動事件 function fnMove(ev){ var oEvent=ev||event; oBox.style.left = oEvent.clientX - disX + 'px'; oBox.style.top = oEvent.clientY - disY + 'px'; } //滑鼠抬起事件 function fnUp(){ document.onmousemove = null; document.onmouseup = null; } </script> </head> <body> <div id="box"></div> </body> </html>
下面是面向物件的程式碼
drag.js
/** * 拖拽 * @param {Object} id div的id */ function Drag(id){ this.oBox = document.getElementById(id); this.disX = 0; this.disY = 0; var _this = this; this.oBox.onmousedown = function(){ _this.fnDown(); } } //滑鼠按下 Drag.prototype.fnDown = function(ev){ var oEvent = ev || event; this.disX = oEvent.clientX - this.oBox.offsetLeft; this.disY = oEvent.clientY - this.oBox.offsetTop; var _this = this; document.onmousemove = function(){ _this.fnMove(); }; document.onmouseup = function(){ _this.fnUp(); }; } //滑鼠移動 Drag.prototype.fnMove = function(ev){ var oEvent= ev || event; this.oBox.style.left = oEvent.clientX - this.disX + 'px'; this.oBox.style.top = oEvent.clientY - this.disY + 'px'; } //滑鼠抬起 Drag.prototype.fnUp = function(){ document.onmousemove = null; document.onmouseup = null; }
drag.html
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <style> div { position: absolute; } </style> <title>拖拽</title> <script type="text/javascript" src="../js/drag.js" ></script> <script> window.onload = function(){ var drag1 = new Drag("box1"); var drag1 = new Drag("box2"); }; </script> </head> <body> <div id="box1" style="background: red;width: 200px;height: 200px;"></div> <div id="box2" style="background: blue;width: 100px;height: 100px;"></div> </body> </html>
此拖拽有一個問題,就是沒有控制拖拽出邊界的問題。但我們又不想去修改程式碼,那我們怎麼做?學過java的應該都知道可以寫一個子類來做一些更加具體的操作,又保留了父類的功能,就是繼承。
html
<script type="text/javascript" src="../js/drag.js" ></script> <script type="text/javascript" src="../js/dragLimit.js" ></script> <script> window.onload = function(){ var drag1 = new Drag("box1"); var drag1 = new DragLimit("box2");//藍色是不會超出邊界的 }; </script> <body> <div id="box1" style="background: red;width: 200px;height: 200px;"></div> <div id="box2" style="background: blue;width: 100px;height: 300px;"></div> </body>
DragLimit.js:DragLimit繼承自Drag,控制了不能出邊界
/** * 限制邊界的拖拽,繼承自Drag * @param {Object} id */ function DragLimit(id){ Drag.call(this,id); } //繼承方法 for(var p in Drag.prototype){ DragLimit.prototype[p] = Drag.prototype[p]; } /** * 覆寫父類的滑鼠移動方法,控制不能移出邊界 */ DragLimit.prototype.fnMove = function(ev){ var oEvent= ev || event; var left = oEvent.clientX - this.disX; var top = oEvent.clientY - this.disY; //控制邊界 if(left < 0){ left = 0; } else if(left > document.documentElement.clientWidth-this.oBox.offsetWidth){ left = document.documentElement.clientWidth-this.oBox.offsetWidth; } if(top <= 0){ top = 0; } else if(top > document.documentElement.clientHeight-this.oBox.offsetHeight){ top = document.documentElement.clientHeight-this.oBox.offsetHeight; } this.oBox.style.left = left + 'px'; this.oBox.style.top = top + 'px'; }
感興趣的朋友可以使用線上HTML/CSS/JavaScript程式碼執行工具:http://tools.jb51.net/code/HtmlJsRun測試上述程式碼執行效果。
更多關於JavaScript相關內容感興趣的讀者可檢視本站專題:《javascript面向物件入門教程》、《JavaScript錯誤與除錯技巧總結》、《JavaScript資料結構與演算法技巧總結》、《JavaScript遍歷演算法與技巧總結》及《JavaScript數學運算用法總結》
希望本文所述對大家JavaScript程式設計有所幫助。