利用JavaScript实现一个飞机弹幕效果

<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title></title> <style type="text/css"> body{ width: 70vw;/*长宽最好是obj的倍数*/ height: 90vh; border-width: 10px; border-style: solid; border-color: blue; line-height:600px;/*文本垂直居中*/ text-align: center;/*文本水平居中*/ position: relative;/*相对定位*/ left: 0px; top: 0px; } /*开场动画*/ @-webkit-keyframes mymove { from {top:50vh;} to {top:100px;} } #obj{ -webkit-animation-name:mymove; -webkit-animation-duration:1s; -webkit-animation-timing-function:linear; position: absolute; left: 30vw; top: 50vh; width: 0px; height: 0px; border-left: 30px solid transparent; border-right: 30px solid transparent; border-bottom: 10px solid red; } div{ text-align: center; line-height:30px; } </style> </head> <body>  <div id='obj'>飞机</div> <button id='start'>开始</button> | <button onclick="stop()">暂停</button> </body> <script type="text/javascript"> var key = document.body.onkeydown =f; //注册keydown事件处理函数 var clientH= document.body.clientHeight;//获取body高 var clientW= document.body.clientWidth;//获取body宽 var obj=document.getElementById('obj');//飞机对象 var borderX=parseInt(getComputedStyle(obj,null).getPropertyValue('border-left')); var borderY=parseInt(getComputedStyle(obj,null).getPropertyValue('border-bottom')); var movePx=10;//飞机每次移动的距离 var speed=500;//雨下落速度 var distance=10;//雨下落距离 var rainleft=0;//弹幕雨x坐标 var raintop=0;//弹幕雨y坐标 //生成雨 function setrain(){ rainleft=parseInt(Math.random()*clientW); raintop=0;//parseInt(Math.random()*clientH); let div=document.createElement('div'); div.className ='div'; div.style.borderRadius='50%'; div.style.width='6px'; div.style.height='10px'; div.style.backgroundColor='pink'; div.style.position = 'absolute'; div.style.left=rainleft + 'px'; div.style.top=raintop + 'px'; document.body.appendChild(div); } //雨下落 function downrain(){ var myTop=parseInt(getComputedStyle(obj,null).getPropertyValue('top'));//获取精灵y坐标 var myLeft=parseInt(getComputedStyle(obj,null).getPropertyValue('left'));//获取精灵x坐标 let div=document.getElementsByClassName('div'); //遍历all雨滴 for(let i=0;i<div.length-1;i++){ let divleft=parseInt(div[i].style.left); let divtop=parseInt(div[i].style.top); div[i].style.top=divtop+distance+'px'; //判断飞机是否被击中 if(Math.abs(divtop-myTop)<borderY && Math.abs(divleft-myLeft)<borderX){ console.log('被击中了 borderY:'+borderY+' borderX:'+borderX); console.log('------- myTop:'+myTop+' myLeft:'+myLeft); console.log('------- rainY:'+divtop+' rainX:'+divleft); stop(); alert('被击中了'); } } } //清除落地的雨 function delrain(){ let div=document.getElementsByClassName('div'); //遍历all雨滴 for(let i=0;i<div.length-1;i++){ // div[i].style.left if(parseInt(div[i].style.top)>clientH){ div[i].parentNode.removeChild(div[i]); }; } } //开始 document.getElementById('start').onclick=start; function start(e){ var e = e || window.event; //标准化事件处理 inter=setInterval((setrain),speed); inter1=setInterval((downrain),speed); inter2=setInterval((delrain),speed); } //暂停 function stop(){ clearInterval(inter); clearInterval(inter1); clearInterval(inter2); } //移动飞机 function f (va) { var e = e || window.event; //标准化事件处理 let s = '';//val.type + " " + val.key; //获取键盘事件类型和按下的值 let key=va.key; var myTop=parseInt(getComputedStyle(obj,null).getPropertyValue('top'));//获取精灵y坐标 parseInt(obj.style.top); var myLeft=parseInt(getComputedStyle(obj,null).getPropertyValue('left'));//获取精灵x坐标 parseInt(obj.style.left); var myWidth=borderX; var myHeight=borderY; var move=0; if(key=='w'){ move=myTop-movePx;//每次移动10 if(move<0 || move>clientH){ return false;//不能超过边界 } obj.style.top=move+'px'; s='上'; } if(key=='s'){ move=myTop+movePx; if(move<0 || move>clientH-myHeight){ return false; } obj.style.top=move+'px'; s='下'; } if(key=='a'){ move=myLeft-movePx; if(move<0 || move>clientW){ return false; } obj.style.left=move+'px'; s='左'; } if(key=='d'){ move=myLeft+movePx; if(move<0 || move>clientW-myWidth){ return false; } obj.style.left=move+'px'; s='右'; } // obj.innerText=s;//设置文本 & 清楚之前的元素 // console.log(move+' top:'+myTop+' left:'+myLeft); } /*f() end--*/ </script> </html>

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