HTML5 canvas如何绘制酷炫能量线条效果（附代码）

上面是效果图，下面直接附js代码，希望对大家有所帮助！！

// UTILconst PI = Math.PI,  TWO_PI = Math.PI * 2;
const Util = {
}
    ;
Util.timeStamp = function() {
      return window.PErformance.now();
}
    ;
Util.random = function(min, max) {
      return min + Math.random() * (max - min);
}
    ;
Util.map = function(a, b, c, d, e) {
      return (a - b) / (c - b) * (e - d) + d;
}
    ;
Util.lerp = function(value1, value2, amount) {
      return value1 + (value2 - value1) * amount;
}
    ;
Util.clamp = function(value, min, max) {
      return Math.max(min, Math.min(max, value));
}
    ;
// Vectorclass Vector {
  constructor(x, y) {
        this.x = x || 0;
        this.y = y || 0;
  }
  set(x, y) {
        this.x = x;
        this.y = y;
  }
  reset() {
        this.x = 0;
        this.y = 0;
  }
  FromAngle(angle) {
        let x = Math.cos(angle),      y = Math.sin(angle);
        return new Vector(x, y);
  }
  add(vector) {
        this.x += vector.x;
        this.y += vector.y;
  }
  sub(vector) {
        this.x -= vector.x;
        this.y -= vector.y;
  }
  mult(scalar) {
        this.x *= scalar;
        this.y *= scalar;
  }
  p(scalar) {
        this.x /= scalar;
        this.y /= scalar;
  }
  dot(vector) {
        return vector.x * this.x + vector.y * this.y;
  }
  limIT(limit_value) {
        if (this.mag() >
     limit_value) this.setMag(limit_value);
  }
  mag() {
        return Math.hypot(this.x, this.y);
  }
  setMag(new_mag) {
        if (this.mag() >
 0) {
          this.normalize();
    }
 else {
          this.x = 1;
          this.y = 0;
    }
        this.mult(new_mag);
  }
  normalize() {
        let mag = this.mag();
        if (mag >
 0) {
          this.x /= mag;
          this.y /= mag;
    }
  }
  heading() {
        return Math.atan2(this.y, this.x);
  }
  setHeading(angle) {
        let mag = this.mag();
        this.x = Math.cos(angle) * mag;
        this.y = Math.sin(angle) * mag;
  }
  dist(vector) {
        return new Vector(this.x - vector.x, this.y - vector.y).mag();
  }
  angle(vector) {
        return Math.atan2(vector.y - this.y, vector.x - this.x);
  }
  copy() {
        return new Vector(this.x, this.y);
  }
}
    // Init canvaslet canvas = document.createElement("canvas"),  ctx = canvas.getContext("2d"),  H = (canvas.height = window.innerHeight),  W = (canvas.width = window.innerWidth);
    document.body.appendChild(canvas);
// Mouselet mouse = {
  x: W/2,  y: H/2}
    ;
canvas.onmouSEMove = function(event) {
      mouse.x = event.clientX - canvas.offsetLeft;
      mouse.y = event.clientY - canvas.offsetTop;
}
    ;
document.body.onresize = function(event){
      H = (canvas.height = window.innerHeight);
      W = (canvas.width = window.innerWidth);
}
// Let's goclass Arrow {
  constructor(x, y, target) {
        this.position = new Vector(x, y);
        this.velocity = new Vector().fromAngle(Util.random(0,TWO_PI));
        this.acceleration = new Vector(0, 0);
        this.target = target;
        this.travelled_distance = 0;
        this.min_size = 1;
        this.max_size = 6;
        this.size = Util.random(this.min_size, this.max_size);
        this.zone = this.size * 4;
        this.topSpeed = Util.map(this.size,this.min_size,this.max_size,40,10);
        let tailLength = Math.floor(Util.map(this.size, this.min_size, this.max_size, 4, 16));
        this.tail = [];
        for (let i = 0;
     i  tailLength;
 i++) {
      this.tail.push({
        x: this.position.x,        y: this.position.y      }
    );
    }
        this.wiggle_speed = Util.map(this.size, this.min_size, this.max_size, 2 , 1.2);
        this.blink_offset = Util.random(0, 100);
    this.alpha = Util.random(0.1,1)  }
  render() {
        this.update();
        this.draw();
  }
  update() {
        let old_position = this.position.copy();
        // Focus on target    let t = new Vector(this.target.x, this.target.y),      angle = this.position.angle(t);
        let d_f_target = t.dist(this.position);
          let f = new Vector().fromAngle(angle);
          f.setMag(Util.map(Util.clamp(d_f_target,0,400), 0, 400, 0, this.topSpeed * 0.1));
          this.adDForce(f);
            // Update position and velocity    this.velocity.add(this.acceleration);
    if(d_f_target  800){
           this.velocity.limit(Util.map(Util.clamp(d_f_target,0,800), 0, 800, this.topSpeed*0.4, this.topSpeed));
       }
else{
             this.velocity.limit(this.topSpeed);
       }
        this.position.add(this.velocity);
        // Reset acceleration for the next loop    this.acceleration.mult(0);
        this.travelled_distance += old_position.dist(this.position);
          let wiggle =        Math.sin(frame * this.wiggle_speed) *        Util.map(this.velocity.mag(), 0, this.topSpeed, 0, this.size);
          let w_a = this.velocity.heading() + Math.PI / 2;
          let w_x = this.position.x + Math.cos(w_a) * wiggle,        w_y = this.position.y + Math.sin(w_a) * wiggle;
          this.travelled_distance = 0;
          let from = this.tail.length - 1,        to = 0;
              let n = new Vector().fromAngle(Util.random(0,TWO_PI));
          n.setMag(Math.random()*this.size);
          VAR tail = {
 x: w_x+ n.x, y: w_y + n.y}
    ;
          this.tail.splice(from, 1);
          this.tail.splice(to, 0, tail);
      }
  draw() {
                let energy = Util.map(this.velocity.mag(),0,this.topSpeed,0.1,1);
            let color =      "hsl("+Math.sin((frame + this.blink_offset) * 0.1) * 360+",50%,"+                Util.map(this.velocity.mag(),0,this.topSpeed,40,100) * this.alpha        +"%)";
        ctx.globalAlpha = this.alpha;
        ctx.strokeStyle = color;
        for (let i = 0;
     i  this.tail.length - 1;
 i++) {
          let t = this.tail[i],        next_t = this.tail[i + 1];
          ctx.lineWidth = Util.map(i, 0, this.tail.length - 1, this.size, 1);
          ctx.beginPath();
          ctx.moveTo(t.x, t.y);
          ctx.lineto(next_t.x, next_t.y);
          ctx.closePath();
          ctx.stroke();
    }
            let gradient_size = 140 * energy;
    var grd = ctx.createRadialGradient(  this.position.x,this.position.y , 5,  this.position.x,this.position.y, gradient_size);
    grd.addColorStop(0, "rgba(255,255,255,0.01)");
    grd.addColorStop(0.1, "rgba(255,120,200,0.02)");
    grd.addColorStop(0.9, "rgba(255,255,120,0)");
    grd.addColorStop(1, "rgba(0,0,0,0)");
    // Fill with gradientctx.fillStyle = grd;
    ctx.fillRect(this.position.x - gradient_size / 2 ,this.position.y - gradient_size / 2 , gradient_size, gradient_size);
             ctx.globalAlpha = energy+0.2;
        ctx.fillStyle = "white";
        for(let i = 0;
     i  4;
 i++){
          let n = new Vector().fromAngle(Util.random(0,TWO_PI));
          n.setMag(Math.random()*energy*100);
          n.add(this.position);
          ctx.beginPath();
          ctx.arc(n.x,n.y,Math.random(),0,TWO_PI)      ctx.fill();
    }
      }
  addForce(vector) {
        this.acceleration.add(vector);
  }
  avoid(others) {
        others.foreach(other =>
 {
      if (other !== this) {
            let dist = this.position.dist(other.position),          max_dist = this.zone + other.size;
            if (max_dist - dist >
= 0) {
              let angle = other.position.angle(this.position);
              let force = new Vector().fromAngle(angle);
              force.setMag(Util.map(dist, 0, max_dist, 2, 0));
              this.addForce(force);
        }
      }
    }
    );
  }
}
    let arrows = [];
    for (let i = 0;
     i  100;
 i++) {
      arrows.push(new Arrow(W / 2, H / 2, mouse));
}
    let frame = 0;
    ctx.strokeStyle = "white";
function loop() {
      ctx.fillStyle="black";
      ctx.globalCompositeoperation = "source-over";
      ctx.globalAlpha = 0.2;
      ctx.fillRect(0, 0, W, H);
      ctx.globalAlpha = 1;
      ctx.globalCompositeOperation = "lighter";
      arrows.forEach(a =>
 {
        a.avoid(arrows);
  }
    );
      arrows.forEach(a =>
 {
        a.render();
  }
    );
      frame += 1;
      requestAnimationFrame(loop);
}
    ctx.lineCap = "round";
    ctx.lineJoin = "round";
    loop();
    

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