Stick.js

class Stick {
  constructor(p1, p2, length) {
    this.startPoint = p1;
    this.endPoint = p2;
    this.stiffness = 2;
    this.color = '#f5476a';
    
    // if the length is not given then calculate the distance based on position
    if (!length) {
      this.length = this.startPoint.pos.dist(this.endPoint.pos);
    } else {
      this.length = length;
    }
    
  }