canvas動畫--五彩繽紛的小球

五彩繽紛的小球wucaibinfen.gif

var canvas = document.getElementById("mycanvas");
var canvas = canvas.getContext("2d");

方法一：ES6 定義類

    class Ball{
        constructor(x,y,r,color,speedx,speedy){
            this.x = x;
            this.y = y;
            this.r = r;
            this.color = color;
            this.speedx = speedx;
            this.speedy = speedy;
        }
        draw(){
            context.beginPath();
            context.fillStyle = this.color;
            context.arc(this.x,this.y,this.r,0,Math.PI*2);
            context.fill();
        }
        move(){
            this.x += this.speedx;
            this.y += this.speedy;
            //碰壁檢測
            if(this.x <= this.r || this.x >= canvas.width - this.r ){
                this.speedx *= -1;
            }
            if(this.y <= this.r || this.y >= canvas. height - this.r){
                this.speedy *= -1;
            }
        }
    }

方法二：ES5 構(gòu)造函數(shù)

        function Ball(x,y,r,color,speedx,speedy){
            this.x = x;
            this.y = y;
            this.r = r;
            this.color = color;
            this.speedx = speedx;
            this.speedy = speedy;
        }
        //畫球的方法
        Ball.prototype.draw = function(){
            context.beginPath();
            context.fillStyle = this.color;
            context.arc(this.x,this.y,this.r,0,Math.PI*2);
            context.fill();
        }
        //球的移動方法
        Ball.prototype.move = function(){
            this.x += this.speedx;
            this.y += this.speedy;
            //碰壁檢測
            if(this.x <= this.r || this.x >= canvas.width - this.r ){
                this.speedx *= -1;
            }
            if(this.y <= this.r || this.y >= canvas. height - this.r){
                this.speedy *= -1;
            }
        }

實例化小球

        function randNum(min,max){
             return parseInt(Math.random()*(max-min)+min);
        }
        function randColor(){
            return "rgb("+randNum(0,256)+","+randNum(0,256)+","+randNum(0,256)+")";
        }
        
        var arr = [];
        for(var i=0;i<80;i++){
            var r = randNum(1,50);
            var x = randNum(r,canvas.width-r);
            var y = randNum(r,canvas.height-r);
            var speedx = randNum(1,5);
            var speedy = randNum(1,5);
            var colors = randColor();
            var newBall = new Ball(x,y,r,colors,speedx,speedy);
            arr.push(newBall);
        }
        
        function act(){
            context.clearRect(0,0,canvas.width,canvas.height);
            for(var i=0;i<arr.length;i++){
                arr[i].draw();
                arr[i].move();
            }
            window.requestAnimationFrame(act);
        }
        act();