js mouse_go_canvas特效

只需要js代码就行，避免id重复

/**
 * id: mouse_go_canvas
 */
 
const fillColor = "#7400a1"	
 
const mouse_go_canvas = document.createElement("canvas")
mouse_go_canvas.setAttribute("id","mouse_go_canvas")
document.querySelector("body").appendChild(mouse_go_canvas)
 
function init(elemid) {
	let canvas = document.getElementById(elemid),
		c = canvas.getContext("2d"),
		w = (canvas.width = window.innerWidth),
		h = (canvas.height = window.innerHeight);
	return {
		c: c,
		canvas: canvas
	};
}
 
class segm {
	constructor(x, y, l) {
		this.b = Math.random() * 1.9 + 0.1;
		this.x0 = x;
		this.y0 = y;
		this.a = Math.random() * 2 * Math.PI;
		this.x1 = this.x0 + l * Math.cos(this.a);
		this.y1 = this.y0 + l * Math.sin(this.a);
		this.l = l;
	}
	update(x, y) {
		this.x0 = x;
		this.y0 = y;
		this.a = Math.atan2(this.y1 - this.y0, this.x1 - this.x0);
		this.x1 = this.x0 + this.l * Math.cos(this.a);
		this.y1 = this.y0 + this.l * Math.sin(this.a);
	}
}
 
class rope {
	constructor(tx, ty, l, b, slq, typ) {
		if (typ == "l") {
			this.res = l / 2;
		} else {
			this.res = l / slq;
		}
		this.type = typ;
		this.l = l;
		this.segm = [];
		this.segm.push(new segm(tx, ty, this.l / this.res));
		for (let i = 1; i < this.res; i++) {
			this.segm.push(
				new segm(this.segm[i - 1].x1, this.segm[i - 1].y1, this.l / this.res)
			);
		}
		this.b = b;
	}
	update(t) {
		this.segm[0].update(t.x, t.y);
		for (let i = 1; i < this.res; i++) {
			this.segm[i].update(this.segm[i - 1].x1, this.segm[i - 1].y1);
		}
	}
	show() {
		if (this.type == "l") {
			c.beginPath();
			for (let i = 0; i < this.segm.length; i++) {
				c.lineTo(this.segm[i].x0, this.segm[i].y0);
			}
			c.lineTo(
				this.segm[this.segm.length - 1].x1,
				this.segm[this.segm.length - 1].y1
			);
			c.strokeStyle = fillColor;
			c.lineWidth = this.b;
			c.stroke();
 
			c.beginPath();
			c.arc(this.segm[0].x0, this.segm[0].y0, 1, 0, 2 * Math.PI);
			c.fillStyle = fillColor;
			c.fill();
 
			c.beginPath();
			c.arc(
				this.segm[this.segm.length - 1].x1,
				this.segm[this.segm.length - 1].y1,
				2,
				0,
				2 * Math.PI
			);
			c.fillStyle = fillColor;
			c.fill();
		} else {
			for (let i = 0; i < this.segm.length; i++) {
				c.beginPath();
				c.arc(this.segm[i].x0, this.segm[i].y0, this.segm[i].b, 0, 2 * Math.PI);
				c.fillStyle = fillColor;
				c.fill();
			}
			c.beginPath();
			c.arc(
				this.segm[this.segm.length - 1].x1,
				this.segm[this.segm.length - 1].y1,
				2, 0, 2 * Math.PI
			);
			c.fillStyle = fillColor;
			c.fill();
		}
	}
}
 
//setting up canvas
let resObj = init("mouse_go_canvas");
let c = resObj.c,
	canvas = resObj.canvas,
	w = (canvas.width = window.innerWidth),
	h = (canvas.height = window.innerHeight),
	ropes = [];
 
//variables definition
let nameOfVariable = "value",
	mouse = {},
	last_mouse = {},
	rl = 50,
	randl = [],
	target = {
		x: w / 2,
		y: h / 2
	},
	last_target = {},
	t = 0,
	q = 10,
	da = [],
	type = "l";
 
for (let i = 0; i < 100; i++) {
	if (Math.random() > 0.25) {
		type = "l";
	} else {
		type = "o";
	}
	ropes.push(
		new rope(
			w / 2,
			h / 2,
			(Math.random() * 1 + 0.5) * 500,
			Math.random() * 0.4 + 0.1,
			Math.random() * 15 + 5,
			type
		)
	);
	randl.push(Math.random() * 2 - 1);
	da.push(0);
}
 
//place for objects in animation
function draw() {
 
	if (mouse.x) {
		target.errx = mouse.x - target.x;
		target.erry = mouse.y - target.y;
	} else {
		target.errx =
			w / 2 +
			(h / 2 - q) *
			Math.sqrt(2) *
			Math.cos(t) /
			(Math.pow(Math.sin(t), 2) + 1) -
			target.x;
		target.erry =
			h / 2 +
			(h / 2 - q) *
			Math.sqrt(2) *
			Math.cos(t) *
			Math.sin(t) /
			(Math.pow(Math.sin(t), 2) + 1) -
			target.y;
	}
 
	target.x += target.errx / 10;
	target.y += target.erry / 10;
 
	t += 0.01;
 
	for (let i = 0; i < ropes.length; i++) {
		if (randl[i] > 0) {
			da[i] += (1 - randl[i]) / 10;
		} else {
			da[i] += (-1 - randl[i]) / 10;
		}
		ropes[i].update({
			x: target.x +
				randl[i] * rl * Math.cos((i * 2 * Math.PI) / ropes.length + da[i]),
			y: target.y +
				randl[i] * rl * Math.sin((i * 2 * Math.PI) / ropes.length + da[i])
		});
		ropes[i].show();
	}
	last_target.x = target.x;
	last_target.y = target.y;
}
 
//mouse position
canvas.addEventListener(
	"mousemove",
	function(e) {
		last_mouse.x = mouse.x;
		last_mouse.y = mouse.y;
 
		mouse.x = e.pageX - this.offsetLeft;
		mouse.y = e.pageY - this.offsetTop;
	},
	false
);
 
canvas.addEventListener("mouseleave", function(e) {
	mouse.x = false;
	mouse.y = false;
});
 
//animation frame
function loop() {
	setTimeout(loop,100)
	c.clearRect(0, 0, w, h);
	draw();
}
 
//window resize
window.addEventListener("resize", function() {
	(w = canvas.width = window.innerWidth),
	(h = canvas.height = window.innerHeight);
	loop();
});
 
//animation runner
setInterval(loop(),1000/60);