如何使用JS實現PC端移動端的刮卡效果
導語：javascript是一門神奇的語言，可以實現諸多效果的設計，下面小編要給大家提供的是如何使用JS實現PC端移動端的刮卡效果，更多詳情請關注應屆畢業生考試網。
具體代碼：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
<title>小月博客刮刮卡案例分享</title>
<script src="/pic/jquery/2.1.4/jquery.min.js"></script>
<style type="text/css">
* {
padding: 0;
margin: 0;
list-style: none;
}
body {
background: #E34830;
position: relative;
}
.banner1 {
display: block;
width: 100%;
/*height: auto;*/
overflow: hidden;
}
.ggl {
position: relative;
width: 85.6%;
height: 90px;
margin: -5px auto;
background: url(img/ggl.png) no-repeat center center;
background-size: 100% 100%;
border: 1px solid blue;
}
.canvas {
position: absolute;
top: 2px;
left: 2.5%;
width: 95%;
height: 82px;
line-height: 82px;
text-align: center;
z-index: 2;
border: 1px solid black;
}
.info {
position: absolute;
top: 2px;
left: 2.5%;
width: 95%;
height: 82px;
text-align: center;
}
.info span {
display: block;
font-size: 18px;
}
#prompt {
line-height: 40px;
}
.btn {
position: relative;
width: 50%;
height: 35px;
line-height: 35px;
background: #df412b;
color: #fff;
border-radius: 5px;
margin: 0 auto;
z-index: 1;
}
.guize {
display: block;
width: 85.6%;
height: auto;
margin: 5% auto 10% auto;
border-radius: 5px;
border: 1px solid black;
}
.num {
width: 90%;
margin: 0 auto;
height: 30px;
line-height: 30px;
text-align: center;
font-size: 14px;
margin-top: 5%;
border: 1px solid black;
}
#ok,
#no {
display: none;
}
.pop {
position: fixed;
left: 0;
top: 0;
z-index: 3;
width: 100%;
height: 100%;
background: rgba(0, 0, 0, 0.6);
display: none;
}
.pop img {
width: 100%;
height: auto;
overflow: hidden;
margin: 15% auto;
}
</style>
<script>
/pic/p>
var t = 0;
/pic/p>
var initialize = function() {
/pic/p>
$('.num1').html(4 - t);
/pic/p>
function getRandomNum(lbound, ubound) {
return (Math.floor(Math.random() * (ubound - lbound)) + lbound);
}
var r = getRandomNum(1, 100);
var btn = document.getElementsByClassName("btn");
for (var i = 0; i < btn.length; i++) {
btn[i].style.zIndex = '1';
}
document.getElementById("no").style.display = "none";
document.getElementById("ok").style.display = "none";
/pic/p>
isOk = 0;
if (r < t * 33) {
document.getElementById("prompt").innerHTML = "恭喜您，中獎了！"
var ok = document.getElementById("ok");
ok.style.display = "block";
/pic/p>
ok.onclick = function() {
window.location.href = "prize.html"
};
} else {
document.getElementById("prompt").innerHTML = "很遺憾，未中獎！"
document.getElementById("no").style.display = "block";
}
};
var c1; /pic/p>
var ctx; /pic/p>
var ismousedown; /pic/p>
var isOk = 0; /pic/p>
var fontem = parseInt(window.getComputedStyle(document.documentElement, null)["font-size"]); /pic/p>
/* 頁面加載后開始初始化畫布 */
window.onload = function() {
initialize();
c1 = document.getElementById("c1");
/pic/p>
/pic/p>
/pic/p>
c1.width = c1.clientWidth;
c1.height = c1.clientHeight;
ctx = c1.getContext("2d");
/pic/p>
c1.addEventListener("mousemove", eventMove, false);
c1.addEventListener("mousedown", eventDown, false);
c1.addEventListener("mouseup", eventUp, false);
/pic/p>
c1.addEventListener('touchstart', eventDown, false);
c1.addEventListener('touchend', eventUp, false);
c1.addEventListener('touchmove', eventMove, false);
/pic/p>
initCanvas();
}
/pic/p>
function initCanvas() {
/pic/p>
/pic/p>
ctx.globalCompositeOperation = "source-over";
ctx.fillStyle = '#aaaaaa';
ctx.fillRect(0, 0, c1.clientWidth, c1.clientHeight);
ctx.fill();
ctx.font = "Bold 30px Arial";
ctx.textAlign = "center";
ctx.fillStyle = "#999999";
ctx.fillText("刮一刮", c1.width / 2, 50);
/pic/p>
/pic/p>
ctx.globalCompositeOperation = 'destination-out';
}
/pic/p>
function eventDown(e) {
e.preventDefault();
ismousedown = true;
}
/pic/p>
function eventUp(e) {
e.preventDefault();
/pic/p>
var a = ctx.getImageData(0, 0, c1.width, c1.height);
var j = 0;
for (var i = 3; i < a.data.length; i += 4) {
if (a.data[i] == 0) j++;
}
/pic/p>
if (j >= a.data.length / 8) {
isOk = 1;
}
ismousedown = false;
}
/pic/p>
function eventMove(e) {
e.preventDefault();
if (ismousedown) {
if (e.changedTouches) {
e = e.changedTouches[e.changedTouches.length - 1];
}
var topY = document.getElementById("top").offsetTop;
var oX = c1.offsetLeft,
oY = c1.offsetTop + topY;
var x = (e.clientX + document.body.scrollLeft || e.pageX) - oX || 0,
y = (e.clientY + document.body.scrollTop || e.pageY) - oY || 0;
/pic/p>
/pic/p>
ctx.beginPath();
ctx.arc(x, y, fontem * 1.2, 0, Math.PI * 2, true);
/pic/p>
/pic/p>
c1.style.display = 'none';
c1.offsetHeight;
c1.style.display = 'inherit';
ctx.fill();
}
if (isOk) {
var btn = document.getElementsByClassName("btn");
for (var i = 0; i < btn.length; i++) {
btn[i].style.zIndex = '3';
}
document.getElementsByClassName("btn")[0].style.zIndex = "3";
}
}
/pic/p>
$("#no").click(function() {
if (t > 3) {
/pic/p>
$('.pop1').show();
$('.pop1 img').click(function() {
$('.pop1').hide();
})
} else {
t++;
/pic/p>
document.getElementById("no").style.display = "none";
document.getElementById("ok").style.display = "none";
window.onload();
initCanvas();
}
});
</script>
</head>
<body>
<img src="img/banner1.png" class="banner1" />
<p class="ggl" id="top">
<p class="info" id="prize">
<span id="prompt"></span>
<span class="btn" id="ok">領取獎品</span>
<span class="btn" id="no">再來一次</span>
</p>
<canvas id="c1" class="canvas"></canvas>
</p>
<p class="num">
您還有<span class="num1"></span>次刮卡機會
</p>
<img src="img/guize.png" class="guize" />
<!-- 遮罩層1抽獎次數已經用完-->
<p class="pop pop1">
<img src="img/pop1.png" />
</p>
<p class="pop pop2">
<img src="img/pop2.png" id="pop2" />
</p>
</body>
</html>
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