OnCollisionEnter is not working: - unity3d

Question

Please Guys help, I am new to Unity and programming:
I have a two Bouncing Ball, tag as BouncingBall1 and BouncingBall2, I want when a bullet hit both to destroy and if the time have not exceeded displaySecond and you have destroy the balls you win, but my problem is the OnCollisionEnter is not working. The part of wining is not working the rest are, my code fragment is below.
function OnCollisionEnter(col.collision) {
if ((displaySecond < 30) && (
col.gameObject.tag ==
BouncingBall1 == null &&
col.gameObject.tag ==
BouncingBall1 == null)) {
print("You have won");
}
}

Answer 1

col.gameObject.tag == BouncingBall1 == null
I think the problem is with the way you check if an object is destroyed. This isn't the way to do it. Also, you're checking if two identical lines of code are identical. So this will always return true if the display second is lower than 30.
Try changing it to
if ( (displaySecond < 30) &&
(col.gameObject.tag == "BouncingBall1") ) {
Debug.Log("You have won!")
}

Answer 2

It sounds like you want keep track of whether each ball has been destroyed and display "You have won" when both have been destroyed. This code is a little crude but should achieve this:
var ball1Destroyed = false;
var ball2Destroyed = false;
...
function OnCollisionEnter(col : Collision) {
if (col.gameObject.tag == "BouncingBall1") {
ball1Destroyed = true;
}
if (col.gameObject.tag == "BouncingBall2") {
ball2Destroyed = true;
}
if (displaySecond < 30 && ball1Destroyed && ball2Destroyed) {
Debug.Log("You have won");
}
}
This code assumes that the only collisions will be between bullets and balls (not between one ball and another), this can be done with collision layers.