学习资料：JavaScript小项目 弹弹球
<style>
#main{
width: 600px;
height:300px;
background: gray;
margin-left: 300px;
position: absolute;
}
#ball {
width: 20px;
height: 20px;
background-color: yellow;
border-radius: 50%;
position: relative;
}
#board{
width: 80px;
height: 10px;
background: red;
position: absolute;
bottom: 0;
left: 450px;
}
</style>
html部分代码：
<div id="main">
<div id="ball" style="left:0;top:0;"> </div>
<div id="board"></div>
</div>
js部分代码：
<script>
var main = document.getElementById('main');
var ball = document.getElementById('ball');
var board = document.getElementById('board');
//设置小球运动速度
ball.speedX = 3;
ball.speedY = 4;
//控制小球运动轨迹
ball.run = function(){
//parseInt：将字符串转换为整数
var left = parseInt(this.style.left) + this.speedX;
var top = parseInt(this.style.top) + this.speedY;
this.style.left = left + 'px';
this.style.top = top + 'px';
this.check( left,top);
}
//检测碰撞实践
ball.check = function(left,top){
if(left <= 0 || left >= 580){
this.turnX();
}
//球撞到上边转向
if(top <= 0){
this.turnY();
}
//小球碰到下边时，未用挡板则输
if(top >= 282){
clearInterval(); //非setInterval
alert("您输了！点击确定再来一局！");
this.init();
}
//碰撞挡板后Y转向
var board_left = parseInt(board.style.left); //挡板的左边距
var board_top = parseInt(board.style.top); //挡板的上边距
if(left >= board_left && left <= board_left+80 && top+20 >=board_top){
this.turnY();
}
}
//控制小球转向
ball.turnX = function(){
this.speedX = -this.speedX;
}
ball.turnY= function(){
this.speedY= -this.speedY;
}
//设置小球移动时间间隔为20ms
var clock = setInterval(function(){
ball.run();
},20)
//移动挡板
main.onmousemove=function(e){
//如果进入非main区，则直接返回，无变化。用于防止鼠标进入红色挡板内发生相对于挡板的移动。
if(e.target!== main){ //严格不等于
return;
}
//假设位置是长方形挡板的底边中点。
board.style.left=e.offsetX-25+'px'; //数字与px（像素）之间不可有空格。
board.style.top=e.offsetY-9+'px';
}
ball.init = function(){
ball.style.left = 0;
ball.style.top = 0;
}
</script>
完整代码
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>弹弹球</title>
<style>
#main{
width: 600px;
height:300px;
background: gray;
margin-left: 300px;
position: absolute;
}
#ball {
width: 20px;
height: 20px;
background-color: yellow;
border-radius: 50%;
position: relative;
}
#board{
width: 80px;
height: 10px;
background: red;
position: absolute;
bottom: 0;
left: 450px;
}
</style>
</head>
<body>
<div id="main">
<div id="ball" style="left:0;top:0;"> </div>
<div id="board"></div>
</div>
<script>
var main = document.getElementById('main');
var ball = document.getElementById('ball');
var board = document.getElementById('board');
//设置小球运动速度
ball.speedX = 3;
ball.speedY = 4;
//控制小球运动轨迹
ball.run = function(){
//parseInt：将字符串转换为整数
var left = parseInt(this.style.left) + this.speedX;
var top = parseInt(this.style.top) + this.speedY;
this.style.left = left + 'px';
this.style.top = top + 'px';
this.check( left,top);
}
//检测碰撞实践
ball.check = function(left,top){
if(left <= 0 || left >= 580){
this.turnX();
}
//球撞到上边转向
if(top <= 0){
this.turnY();
}
//小球碰到下边时，未用挡板则输
if(top >= 282){
clearInterval(); //非setInterval
alert("您输了！点击确定再来一局！");
this.init();
}
//碰撞挡板后Y转向
var board_left = parseInt(board.style.left); //挡板的左边距
var board_top = parseInt(board.style.top); //挡板的上边距
if(left >= board_left && left <= board_left+80 && top+20 >=board_top){
this.turnY();
}
}
//控制小球转向
ball.turnX = function(){
this.speedX = -this.speedX;
}
ball.turnY= function(){
this.speedY= -this.speedY;
}
//设置小球移动时间间隔为20ms
var clock = setInterval(function(){
ball.run();
},20)
//移动挡板
main.onmousemove=function(e){
//如果进入非main区，则直接返回，无变化。用于防止鼠标进入红色挡板内发生相对于挡板的移动。
if(e.target!== main){ //严格不等于
return;
}
//假设位置是长方形挡板的底边中点。
board.style.left=e.offsetX-25+'px'; //数字与px（像素）之间不可有空格。
board.style.top=e.offsetY-9+'px';
}
ball.init = function(){
ball.style.left = 0;
ball.style.top = 0;
}
</script>
</body>
</html>
