JAVASCRIPT

javascript detect collision

if (rect1.x < rect2.x + rect2.width &&
   rect1.x + rect1.width > rect2.x &&
   rect1.y < rect2.y + rect2.height &&
   rect1.y + rect1.height > rect2.y) {
    // collision detected!
}

javascript check collision

if(ball.y > rect.y - rect.height &&
   ball.x > rect.x - rect.widht &&
   ball.x < rect.x + rect.widht){
	vel.y *= -1;
  //collision check for pong game
}

js check collision

if (rect1.x < rect2.x + rect2.w &&
        rect1.x + rect1.w > rect2.x &&
        rect1.y < rect2.y + rect2.h &&
        rect1.h + rect1.y > rect2.y) {
        // collision detected!
        }