how do I make a point system in javascript?

Question

ive made a ping pong game and i want to make it so when it hits the top/bottom of the screen you get a point and it shows your points but i cant manage to do that. (this is my code btw)
var animate = window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
function(callback) { window.setTimeout(callback, 1000/60) };
var canvas = document.createElement('canvas');
var width = 400;
var height = 600;
canvas.width = width;
canvas.height = height;
var context = canvas.getContext('2d');
window.onload = function() {
document.body.appendChild(canvas);
animate(step);
};
var step = function() {
update();
render();
animate(step);
};
var update = function() {
};

function Paddle(x, y, width, height) {
this.x = x;
this.y = y;
this.width = width;
this.height = height;
this.x_speed = 0;
this.y_speed = 0;
}

Paddle.prototype.render = function() {
context.fillStyle = "#000FFF";
context.fillRect(this.x, this.y, this.width, this.height);
};
function Player() {
this.paddle = new Paddle(175, 580, 50, 10);
}

function Computer() {
this.paddle = new Paddle(175, 10, 50, 10);
}
Player.prototype.render = function() {
this.paddle.render();
};

Computer.prototype.render = function() {
this.paddle.render();
};
function Ball(x, y) {
this.x = x;
this.y = y;
this.x_speed = 0;
this.y_speed = 3;
this.radius = 5;
}

Ball.prototype.render = function() {
context.beginPath();
context.arc(this.x, this.y, this.radius, 2 * Math.PI, false);
context.fillStyle = "#00ffd8";
context.fill();
};
var player = new Player();
var computer = new Computer();
var ball = new Ball(200, 300);

var render = function() {
context.fillStyle = "#ff7700";
context.fillRect(0, 0, width, height);
player.render();
computer.render();
ball.render();
};
var update = function() {
ball.update();
};

Ball.prototype.update = function() {
this.x += this.x_speed;
this.y += this.y_spe

Answer 1

youll need to create an ongoing loop that adds ++ to a variable everytime an if occurs.

Answer 2

Lol thx