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
}

javascript collision detection

function checkCollisions(x1, y1, w1, h1, x2, y2, w2, h2){
	if (x1 + w1 >= x2 && x1 + w1 <= x2 + w2 && y1 + h1 >= y2 && y1 + h1 <= y2 + h2) {
		return true;
	} else if (x1 >= x2 && x1 <= x2 + w2 && y1 >= y2 && y1 <= y2 + h2) {
		return true;
	} else {
		return false;
	}
}

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!
        }