小编这次要给大家分享的是js如何实现抽奖转盘，文章内容丰富，感兴趣的小伙伴可以来了解一下，希望大家阅读完这篇文章之后能够有所收获。
HTML 这里.left 固定了圆的宽度和高度，还有canvas也设置了固定宽高 绘制圆心的坐标也就出来了 (203,203)
抽奖转盘是由一个大圆和一个内圆完成 ；大圆负责绘制上奖品 ，内圆负责确定指针的位置，指针直接使用图片，决定位置确定
<div class="left"> <div class="turnplate" > <canvas class="item" id="wheelcanvas" width="406px" height="406px"></canvas> <img class="pointer" src="sp2/point.png"/> </div> </div>
外圆留空多少的问题
PS里查看间距是多少，此处圆心(203,203) 大圆的半径就是203-10 =193
这个数值在下图里设置
JS
<script type="text/javascript">
var turnplate={
restaraunts:[], //大转盘奖品名称
colors:[], //大转盘奖品区块对应背景颜色
outsideRadius:193, //大转盘外圆的半径 192
textRadius:155, //大转盘奖品位置距离圆心的距离
insideRadius:68, //大转盘内圆的半径
startAngle:0, //开始角度
bRotate:false //false:停止;ture:旋转
};
$(document).ready(function(){
//动态添加大转盘的奖品与奖品区域背景颜色
turnplate.restaraunts = ["50元代金券", "升职加薪", "100元代金券", "财源滚滚", "200元代金券", "爱情甜蜜 ", "500元代金券", "变美变帅"];
turnplate.colors = ["#1b62ca", "#1bacff", "#1b62ca", "#1bacff","#1b62ca", "#1bacff", "#1b62ca", "#1bacff"];
var rotateTimeOut = function (){
$('#wheelcanvas').rotate({
angle:0,
animateTo:2160,
duration:8000,
callback:function (){
alert('网络超时，请检查您的网络设置！');
}
});
};
//旋转转盘 item:奖品位置; txt：提示语;
var rotateFn = function (item, txt){
var angles = item * (360 / turnplate.restaraunts.length) - (360 / (turnplate.restaraunts.length*2));
if(angles<270){
angles = 270 - angles;
}else{
angles = 360 - angles + 270;
}
$('#wheelcanvas').stopRotate();
$('#wheelcanvas').rotate({
angle:0,
animateTo:angles+1800,
duration:8000,
callback:function (){
alert(txt);
turnplate.bRotate = !turnplate.bRotate;
}
});
};
$('.pointer').click(function (){
if(turnplate.bRotate)return;
turnplate.bRotate = !turnplate.bRotate;
//获取随机数(奖品个数范围内)
var item = rnd(1,turnplate.restaraunts.length);
//奖品数量等于10,指针落在对应奖品区域的中心角度[252, 216, 180, 144, 108, 72, 36, 360, 324, 288]
rotateFn(item, turnplate.restaraunts[item-1]);
/* switch (item) {
case 1:
rotateFn(252, turnplate.restaraunts[0]);
break;
case 2:
rotateFn(216, turnplate.restaraunts[1]);
break;
case 3:
rotateFn(180, turnplate.restaraunts[2]);
break;
case 4:
rotateFn(144, turnplate.restaraunts[3]);
break;
case 5:
rotateFn(108, turnplate.restaraunts[4]);
break;
case 6:
rotateFn(72, turnplate.restaraunts[5]);
break;
case 7:
rotateFn(36, turnplate.restaraunts[6]);
break;
case 8:
rotateFn(360, turnplate.restaraunts[7]);
break;
case 9:
rotateFn(324, turnplate.restaraunts[8]);
break;
case 10:
rotateFn(288, turnplate.restaraunts[9]);
break;
} */
console.log(item);
});
});
function rnd(n, m){
var random = Math.floor(Math.random()*(m-n+1)+n);
return random;
}
//页面所有元素加载完毕后执行drawRouletteWheel()方法对转盘进行渲染
window.onload=function(){
drawRouletteWheel();
};
function drawRouletteWheel() {
var canvas = document.getElementById("wheelcanvas");
if (canvas.getContext) {
//根据奖品个数计算圆周角度
var arc = Math.PI / (turnplate.restaraunts.length/2);//圆周率/ 奖品数量除以2
var ctx = canvas.getContext("2d");
//在给定矩形内清空一个矩形
ctx.clearRect(0,0,422,422);
//strokeStyle 属性设置或返回用于笔触的颜色、渐变或模式
ctx.strokeStyle = "#FFBE04";
//font 属性设置或返回画布上文本内容的当前字体属性
ctx.font = '16px Microsoft YaHei';
// 绘制圆 （弧形）
for(var i = 0; i < turnplate.restaraunts.length; i++) {
var angle = turnplate.startAngle + i * arc;
ctx.fillStyle = turnplate.colors[i];
ctx.beginPath();
//arc(x,y,r,起始角,结束角,绘制方向) 方法创建弧/曲线（用于创建圆或部分圆）
ctx.arc(203, 203, turnplate.outsideRadius, angle, angle + arc, false);//绘制外圆
ctx.arc(203, 203, turnplate.insideRadius, angle + arc, angle, true);//绘制内圆
ctx.stroke();
ctx.fill();
//锁画布(为了保存之前的画布状态)
ctx.save();
//----绘制奖品开始----
ctx.fillStyle = "#FFF";/*奖品文字颜色*/
var text = turnplate.restaraunts[i];
var line_height = 17;
//translate方法重新映射画布上的 (0,0) 位置
ctx.translate(211 + Math.cos(angle + arc / 2) * turnplate.textRadius, 211 + Math.sin(angle + arc / 2) * turnplate.textRadius);
//rotate方法旋转当前的绘图
ctx.rotate(angle + arc / 2 + Math.PI / 2);
/** 下面代码根据奖品类型、奖品名称长度渲染不同效果，如字体、颜色、图片效果。(具体根据实际情况改变) **/
if(text.indexOf("M")>0){//流量包
var texts = text.split("M");
for(var j = 0; j<texts.length; j++){
ctx.font = j == 0?'bold 20px Microsoft YaHei':'16px Microsoft YaHei';
if(j == 0){
ctx.fillText(texts[j]+"M", -ctx.measureText(texts[j]+"M").width / 2, j * line_height);
}else{
ctx.fillText(texts[j], -ctx.measureText(texts[j]).width / 2, j * line_height);
}
}
}else if(text.indexOf("M") == -1 && text.length>6){//奖品名称长度超过一定范围
text = text.substring(0,6)+"||"+text.substring(6);
var texts = text.split("||");
for(var j = 0; j<texts.length; j++){
ctx.fillText(texts[j], -ctx.measureText(texts[j]).width / 2, j * line_height);
}
}else{
//在画布上绘制填色的文本。文本的默认颜色是黑色
//measureText()方法返回包含一个对象，该对象包含以像素计的指定字体宽度
ctx.fillText(text, -ctx.measureText(text).width / 2, 0);
}
//添加对应图标
if(text.indexOf("闪币")>0){
var img= document.getElementById("shan-img");
img.onload=function(){
ctx.drawImage(img,-15,10);
};
ctx.drawImage(img,-15,10);
}else if(text.indexOf("谢谢参与")>=0){
var img= document.getElementById("sorry-img");
img.onload=function(){
ctx.drawImage(img,-15,10);
};
ctx.drawImage(img,-15,10);
}
//把当前画布返回（调整）到上一个save()状态之前
ctx.restore();
//----绘制奖品结束----
}
}
}
</script>引用jquery
在加载以下JS
/* ????????????? www.datouwang.com */
(function($) {
var supportedCSS,styles=document.getElementsByTagName("head")[0].style,toCheck="transformProperty WebkitTransform OTransform msTransform MozTransform".split(" ");
for (var a=0;a<toCheck.length;a++) if (styles[toCheck[a]] !== undefined) supportedCSS = toCheck[a];
// Bad eval to preven google closure to remove it from code o_O
// After compresion replace it back to var IE = 'v' == '\v'
var IE = eval('"v"=="\v"');
jQuery.fn.extend({
rotate:function(parameters)
{
if (this.length===0||typeof parameters=="undefined") return;
if (typeof parameters=="number") parameters={angle:parameters};
var returned=[];
for (var i=0,i0=this.length;i<i0;i++)
{
var element=this.get(i);
if (!element.Wilq32 || !element.Wilq32.PhotoEffect) {
var paramClone = $.extend(true, {}, parameters);
var newRotObject = new Wilq32.PhotoEffect(element,paramClone)._rootObj;
returned.push($(newRotObject));
}
else {
element.Wilq32.PhotoEffect._handleRotation(parameters);
}
}
return returned;
},
getRotateAngle: function(){
var ret = [];
for (var i=0,i0=this.length;i<i0;i++)
{
var element=this.get(i);
if (element.Wilq32 && element.Wilq32.PhotoEffect) {
ret[i] = element.Wilq32.PhotoEffect._angle;
}
}
return ret;
},
stopRotate: function(){
for (var i=0,i0=this.length;i<i0;i++)
{
var element=this.get(i);
if (element.Wilq32 && element.Wilq32.PhotoEffect) {
clearTimeout(element.Wilq32.PhotoEffect._timer);
}
}
}
});
// Library agnostic interface
Wilq32=window.Wilq32||{};
Wilq32.PhotoEffect=(function(){
if (supportedCSS) {
return function(img,parameters){
img.Wilq32 = {
PhotoEffect: this
};
this._img = this._rootObj = this._eventObj = img;
this._handleRotation(parameters);
}
} else {
return function(img,parameters) {
// Make sure that class and id are also copied - just in case you would like to refeer to an newly created object
this._img = img;
this._rootObj=document.createElement('span');
this._rootObj.style.display="inline-block";
this._rootObj.Wilq32 =
{
PhotoEffect: this
};
img.parentNode.insertBefore(this._rootObj,img);
if (img.complete) {
this._Loader(parameters);
} else {
var self=this;
// TODO: Remove jQuery dependency
jQuery(this._img).bind("load", function()
{
self._Loader(parameters);
});
}
}
}
})();
Wilq32.PhotoEffect.prototype={
_setupParameters : function (parameters){
this._parameters = this._parameters || {};
if (typeof this._angle !== "number") this._angle = 0 ;
if (typeof parameters.angle==="number") this._angle = parameters.angle;
this._parameters.animateTo = (typeof parameters.animateTo==="number") ? (parameters.animateTo) : (this._angle);
this._parameters.step = parameters.step || this._parameters.step || null;
this._parameters.easing = parameters.easing || this._parameters.easing || function (x, t, b, c, d) { return -c * ((t=t/d-1)*t*t*t - 1) + b; }
this._parameters.duration = parameters.duration || this._parameters.duration || 1000;
this._parameters.callback = parameters.callback || this._parameters.callback || function(){};
if (parameters.bind && parameters.bind != this._parameters.bind) this._BindEvents(parameters.bind);
},
_handleRotation : function(parameters){
this._setupParameters(parameters);
if (this._angle==this._parameters.animateTo) {
this._rotate(this._angle);
}
else {
this._animateStart();
}
},
_BindEvents:function(events){
if (events && this._eventObj)
{
// Unbinding previous Events
if (this._parameters.bind){
var oldEvents = this._parameters.bind;
for (var a in oldEvents) if (oldEvents.hasOwnProperty(a))
// TODO: Remove jQuery dependency
jQuery(this._eventObj).unbind(a,oldEvents[a]);
}
this._parameters.bind = events;
for (var a in events) if (events.hasOwnProperty(a))
// TODO: Remove jQuery dependency
jQuery(this._eventObj).bind(a,events[a]);
}
},
_Loader:(function()
{
if (IE)
return function(parameters)
{
var width=this._img.width;
var height=this._img.height;
this._img.parentNode.removeChild(this._img);
this._vimage = this.createVMLNode('image');
this._vimage.src=this._img.src;
this._vimage.style.height=height+"px";
this._vimage.style.width=width+"px";
this._vimage.style.position="absolute"; // FIXES IE PROBLEM - its only rendered if its on absolute position!
this._vimage.style.top = "0px";
this._vimage.style.left = "0px";
/* Group minifying a small 1px precision problem when rotating object */
this._container = this.createVMLNode('group');
this._container.style.width=width;
this._container.style.height=height;
this._container.style.position="absolute";
this._container.setAttribute('coordsize',width-1+','+(height-1)); // This -1, -1 trying to fix ugly problem with small displacement on IE
this._container.appendChild(this._vimage);
this._rootObj.appendChild(this._container);
this._rootObj.style.position="relative"; // FIXES IE PROBLEM
this._rootObj.style.width=width+"px";
this._rootObj.style.height=height+"px";
this._rootObj.setAttribute('id',this._img.getAttribute('id'));
this._rootObj.className=this._img.className;
this._eventObj = this._rootObj;
this._handleRotation(parameters);
}
else
return function (parameters)
{
this._rootObj.setAttribute('id',this._img.getAttribute('id'));
this._rootObj.className=this._img.className;
this._width=this._img.width;
this._height=this._img.height;
this._widthHalf=this._width/2; // used for optimisation
this._heightHalf=this._height/2;// used for optimisation
var _widthMax=Math.sqrt((this._height)*(this._height) + (this._width) * (this._width));
this._widthAdd = _widthMax - this._width;
this._heightAdd = _widthMax - this._height; // widthMax because maxWidth=maxHeight
this._widthAddHalf=this._widthAdd/2; // used for optimisation
this._heightAddHalf=this._heightAdd/2;// used for optimisation
this._img.parentNode.removeChild(this._img);
this._aspectW = ((parseInt(this._img.style.width,10)) || this._width)/this._img.width;
this._aspectH = ((parseInt(this._img.style.height,10)) || this._height)/this._img.height;
this._canvas=document.createElement('canvas');
this._canvas.setAttribute('width',this._width);
this._canvas.style.position="relative";
this._canvas.style.left = -this._widthAddHalf + "px";
this._canvas.style.top = -this._heightAddHalf + "px";
this._canvas.Wilq32 = this._rootObj.Wilq32;
this._rootObj.appendChild(this._canvas);
this._rootObj.style.width=this._width+"px";
this._rootObj.style.height=this._height+"px";
this._eventObj = this._canvas;
this._cnv=this._canvas.getContext('2d');
this._handleRotation(parameters);
}
})(),
_animateStart:function()
{
if (this._timer) {
clearTimeout(this._timer);
}
this._animateStartTime = +new Date;
this._animateStartAngle = this._angle;
this._animate();
},
_animate:function()
{
var actualTime = +new Date;
var checkEnd = actualTime - this._animateStartTime > this._parameters.duration;
// TODO: Bug for animatedGif for static rotation ? (to test)
if (checkEnd && !this._parameters.animatedGif)
{
clearTimeout(this._timer);
}
else
{
if (this._canvas||this._vimage||this._img) {
var angle = this._parameters.easing(0, actualTime - this._animateStartTime, this._animateStartAngle, this._parameters.animateTo - this._animateStartAngle, this._parameters.duration);
this._rotate((~~(angle*10))/10);
}
if (this._parameters.step) {
this._parameters.step(this._angle);
}
var self = this;
this._timer = setTimeout(function()
{
self._animate.call(self);
}, 10);
}
// To fix Bug that prevents using recursive function in callback I moved this function to back
if (this._parameters.callback && checkEnd){
this._angle = this._parameters.animateTo;
this._rotate(this._angle);
this._parameters.callback.call(this._rootObj);
}
},
_rotate : (function()
{
var rad = Math.PI/180;
if (IE)
return function(angle)
{
this._angle = angle;
this._container.style.rotation=(angle%360)+"deg";
}
else if (supportedCSS)
return function(angle){
this._angle = angle;
this._img.style[supportedCSS]="rotate("+(angle%360)+"deg)";
}
else
return function(angle)
{
this._angle = angle;
angle=(angle%360)* rad;
// clear canvas
this._canvas.width = this._width+this._widthAdd;
this._canvas.height = this._height+this._heightAdd;
// REMEMBER: all drawings are read from backwards.. so first function is translate, then rotate, then translate, translate..
this._cnv.translate(this._widthAddHalf,this._heightAddHalf); // at least center image on screen
this._cnv.translate(this._widthHalf,this._heightHalf); // we move image back to its orginal
this._cnv.rotate(angle); // rotate image
this._cnv.translate(-this._widthHalf,-this._heightHalf); // move image to its center, so we can rotate around its center
this._cnv.scale(this._aspectW,this._aspectH); // SCALE - if needed ;)
this._cnv.drawImage(this._img, 0, 0); // First - we draw image
}
})()
}
if (IE)
{
Wilq32.PhotoEffect.prototype.createVMLNode=(function(){
document.createStyleSheet().addRule(".rvml", "behavior:url(#default#VML)");
try {
!document.namespaces.rvml && document.namespaces.add("rvml", "urn:schemas-microsoft-com:vml");
return function (tagName) {
return document.createElement('<rvml:' + tagName + ' class="rvml">');
};
} catch (e) {
return function (tagName) {
return document.createElement('<' + tagName + ' xmlns="urn:schemas-microsoft.com:vml" class="rvml">');
};
}
})();
}
})(jQuery);看完这篇关于js如何实现抽奖转盘的文章，如果觉得文章内容写得不错的话，可以把它分享出去给更多人看到。
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