人物行走
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代码
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>键盘事件控制人物行走-前端猫</title> <style> * { padding: 0; margin: 0; } #app { position: relative; width: 800px; height: 500px; border: 2px solid green; margin: 0 auto; } #box { position: absolute; left: 100px; top: 0; width: 31.75px; height: 47.75px; background-image: url("./img/go.jpg"); background-repeat: no-repeat; background-position: 0 0; } </style> </head> <body> <div id="app"> <div id="box"></div> </div> </body> <script> var box = document.querySelector("#box"); var iLeft = 0; var iTop = 0;// 0 向下 -1向左 -2向右 -3向上 var timer; function move() { iLeft--; if (iLeft < -3) iLeft = 0; box.style.backgroundPositionX = (iLeft * 31.75) + "px"; box.style.backgroundPositionY = (iTop * 47.75) + "px"; } function go() { // 如果成立说明已经拥有定时器,不成立则没有定时器 if (!timer) { move(); timer = setInterval(move, 300); document.onkeyup = function () { //清除定时器 timer = clearInterval(timer); box.style.backgroundPositionX = "0px"; document.onkeyup = null; } } } // 增加键盘事件 document.onkeydown = function (e) { e.preventDefault(); // keycode(37向左,38向上,39向右,40向下) switch (e.keyCode) { case 37: // 向左 iTop = -1; box.style.left = Math.max(box.offsetLeft - 1, 0) + "px"; go(); break; case 38: // 38向上 iTop = -3; box.style.top = Math.max(box.offsetTop - 1, 0) + "px"; go(); break; case 39: // 39向右 iTop = -2; box.style.left = Math.min(box.offsetLeft + 1, app.clientWidth - box.offsetWidth) + "px"; go(); break; case 40: // 40向下 iTop = 0; box.style.top = Math.min(box.offsetTop + 1, app.clientHeight - box.offsetHeight) + "px"; go(); break; } } </script> </html>
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