<!doctype html>

<html>

<head>

<meta charset="utf-8">

<title>无标题文档</title>

<style>

#canvas { border:solid 1px #ccc;}

</style>

</head>

<script src="sprite.js"></script>

<body>

<canvas id="canvas" width="600" height="600"></canvas>

<script>

var canvas = document.getElementById("canvas");

var context = canvas.getContext("2d"),

CLOCK_RADIUS = canvas.width/2 -15 ,

hour_hand_truncation =35,

ballPainter = {   //画小球

    paint:function(sprite,context){

        var x =sprite.left +sprite.width/2,

        y = sprite.top +sprite.height/2,

        width = sprite.width,

        height = sprite.height,

        radius = sprite.width/2;

        context.save();

        context.beginPath();

        context.arc(x,y,radius,0,Math.PI*2,false);

        context.clip();

        context.shadowColor = "rgb(0,0,0)";

        context.shadowOffsetX = -4;

        context.shadowOffsetY = -4;

        context.shadowBlur = 8;

        context.fillStyle = "rgba(218,165,32,0.1)";

        context.fill();

        context.lineWidth =2;

        context.strokeStyle = "rgb(100,100,195)";

        context.stroke();

        context.restore();

        }

    },

ball =  new Sprite("ball",ballPainter);

// 画网格

function drawGrid(color,stepx,stepy){

    context.strokeStyle = color;

    context.lineWidth =0.5;

    for(var i =stepx +0.5;i<canvas.width;i+=stepx){

        context.beginPath();

        context.moveTo(i,0);

        context.lineTo(i,canvas.height);

        context.stroke();

        }

    for(var  i =stepx +0.5;i<canvas.height;i+=stepx){

        context.beginPath();

        context.moveTo(0,i);

        context.lineTo(canvas.width,i);

        context.stroke();

        }

    }

//画指针函数

function drawHand(loc,isHour){

    var angle = (Math.PI *2 )*(loc/60) - Math.PI/2,

    handRadius = isHour ? CLOCK_RADIUS - hour_hand_truncation : CLOCK_RADIUS,

    lineEnd = {

        x:canvas.width/2 + Math.cos(angle)*(handRadius - ball.width /2),

        y:canvas.height/2 +Math.sin(angle)*(handRadius - ball.width /2)

        };

    context.beginPath();

    context.moveTo(canvas.width/2,canvas.height/2);

    context.lineTo(lineEnd.x , lineEnd.y);

    context.stroke();

    ball.left = canvas.width/2 + Math.cos(angle)*handRadius - ball.width/2;

    ball.top = canvas.height/2 + Math.sin(angle)*handRadius - ball.height/2;

    ball.paint(context);

}

function drawClock (){

    drawClockFace();

    drawHands();

    }

// 画多个指针

function drawHands(){

    var date = new Date(),

    hour = date.getHours();

    ball.width = 20;

    ball.height =20;

    drawHand(date.getSeconds(),false);

    hour = hour >12 ? hour -12 :hour ;

    ball.width = 35;

    ball.height = 35 ;

    drawHand(date.getMinutes() ,false );

    ball.width =50;

    ball.height =50;

    drawHand(hour*5 +(date.getMinutes()/60)*5);

    ball.width =10;

    ball.height =10 ;

    ball.left = canvas.width/2 - ball.width/2;

    ball.top =  canvas.height /2 - ball.height/2 ;

    ballPainter.paint(ball,context);

    }

// 画表盘

function drawClockFace(){

    context.beginPath();

    context.arc(canvas.width/2,canvas.height/2,CLOCK_RADIUS,0,Math.PI*2,false );

    context.save();

    context.strokeStyle = "rgba(0,0,0,0.2)";

    context.stroke();

    context.restore();

}

//　运动函数

function animate(){

    context.clearRect(0,0,canvas.width,canvas.height);

    drawGrid("lightgray",10,10);

    drawClock();

    window.requestNextAnimationFrame(animate);

    }

context.lineWidth =0.5;

context.strokeStyle = "rgba(0,0,0,0.2)";

context.shadowColor = "rgba(0,0,0,0.5)";

context.shadowOffsetX =2;

context.shadowOffsetY = 2;

context.shadowBlur =4;

context.stroke();

window.requestNextAnimationFrame(animate);

drawGrid("lightgray",10,10);

</script>

</body>

</html>

sprite  js

var Sprite = function (name,painter,behaviors){

    if(name!== undefined){this.name = name }

    if(painter!== undefined){this.painter = painter}

    this.top =0;

    this.left =0;

    this.width =10;

    this.height = 10;

    this.velocityX = 0;

    this.velocityY =0;

    this.visible = true;

    this.animating = false ;

    this.behaviors = behaviors || [] ;

    return this ;

}

Sprite.prototype = {

    paint:function (context){

        if(this.painter !== undefined && this.visible){

            this.painter.paint(this,context);

            }

        },

    update:function(context,time){

        for(var i=0;i<this.behaviors.length;++i){

            this.behaviors[i].execute(this,context,time);

            }

        }

    }

window.requestNextAnimationFrame = (function(){

    var originalWebkitMethod, wrapper = undefined,callback = undefined,

    geckoVersion = 0 , userAgent = navigator.userAgent, index =0 , self =this;

    if(window.webkitRequestAnimationFrame){

        wrapper = function (time){

            if(time === undefined ){

                time = +new Date();

                }

                self.callback(time);

            };

        originalWebkitMethod = window.webkitRequestAnimationFrame;

        window.webkitRequestAnimationFrame = function (callback,element){

            self.callback = callback ;

            originalWebkitMethod(wrapper,element);

            }

        }

    if(window.mozRequestAnimationFrame){

        index = userAgent.indexOf("rv:");

        if(userAgent.indexOf("GecKo") != -1){

            geckoVersion = userAgent.substr(index +3 ,3);

            if(geckoVersion ==="2.0"){

                window.mozRequestAnimationFrame = undefined ;

                }

            }

        }

return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame ||window.msRequestAnimationFrame || function (callback,element){

        var start,finish;

        window.setTimeout(function(){

            start = +new Date();

            callback(start);

            finish = +new Date();

            self.timeout = 1000/60 - (finish -start);

            },self.timeout);

        }

    })()

    // JavaScript Document

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