canvas鼠标和触摸事件

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html

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JavaScript

var canvas = document.querySelector('canvas');
canvas.height = window.innerHeight;
canvas.width = window.innerWidth;
c = canvas.getContext('2d');

window.addEventListener('resize', function(){
    canvas.height = window.innerHeight;
    canvas.width = window.innerWidth;

initCanvas();
})

function Circle(x, y, radius, vx, vy, rgb, opacity, birth, life){
    this.x = x;
    this.y = y;
    this.radius = radius;
    this.minRadius = radius;
    this.vx = vx;
    this.vy = vy;
    this.birth = birth;
    this.life = life;
    this.opacity = opacity;

this.draw = function() {
        c.beginPath();
        c.arc(this.x, this.y, this.radius, Math.PI * 2, false);
        c.fillStyle = 'rgba(' + rgb +','+ this.opacity +')';
        c.fill();
    }

this.update = function(){
        if (this.x + this.radius > innerWidth || this.x - this.radius < 0) {
            this.vx = -this.vx;
        }

if (this.y + this.radius > innerHeight || this.y - this.radius < 0) {
            this.vy = -this.vy;
        }

this.x += this.vx;
        this.y += this.vy;

this.opacity = 1- (((frame - this.birth) * 1) / this.life);

if (frame > this.birth + this.life){
            for (let i = 0; i < circleArray.length; i++){
                if (this.birth == circleArray[i].birth && this.life == circleArray[i].life){
                    circleArray.splice(i, 1);
                    break;
                }
            }
        } else{
            this.draw();
        }
    }

}

var circleArray = [];

function initCanvas() {
    circleArray = [];
}

var colorArray = [
    '355,85,80',
    '9,80,100',
    '343,81,45'
]

function drawCircles(){
    for (let i = 0; i < 6; i++) {
        let radius = Math.floor(Math.random() * 4) + 2;
        let vx = (Math.random() * 2) - 1;
        let vy = (Math.random() * 2) - 1;
        let spawnFrame = frame;
        let rgb = colorArray[Math.floor(Math.random() * colorArray.length)];
        let life = 100;
        circleArray.push(new Circle(mouse.x, mouse.y, radius, vx, vy, rgb, 1, spawnFrame, life));

}
}

var frame = 0;
function animate() {
    requestAnimationFrame(animate);
    frame += 1;
    c.clearRect(0, 0, innerWidth, innerHeight);
    for (let i = 0; i < circleArray.length; i++ ){
        circleArray[i].update();
    }
    
}

initCanvas();
animate();

// This is just for demo purposes :
for (let i = 1; i < 110; i++) {
    (function (index) {
        setTimeout(function () { 
            mouse.x = 100 + i * 10;
            mouse.y = 100;
            drawCircles();
         }, i * 10);
    })(i);
}

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