how to apply gavity to code in javascript

 function component(width, height, color, x, y, type) {
  this.type = type;
  this.width = width;
  this.height = height;

    this.x = x;
  this.y = y; 
  this.speedX = 0;
  this.speedY = 0; 

    this.gravity = 0.05;
  this.gravitySpeed = 0;
  this.update = function() {
    ctx = myGameArea.context;
    ctx.fillStyle = color;
    ctx.fillRect(this.x, this.y, this.width, this.height);

    }
  this.newPos = function() {
    this.gravitySpeed += this.gravity;

      this.x += this.speedX;
    this.y += this.speedY + this.gravitySpeed; 

    }

 }