Blackjack
Play the game or view thesource code.
1. Starting a Round
The startRound() function first does a little housekeeping.This involves resetting the hands from the previous round, enabling anddisabling form buttons and checking if a new deck is needed.
function startRound() { var i; // Reset all hands. dealer.reset(); for (i = 0; i < player.length; i++) { player[i].reset(); if (i > 0) player[i].fieldNode.style.display = "none"; } // Start with a single player hand. curPlayerHand = 0; numPlayerHands = 1; // Enable/disable buttons. document.forms["controls"].elements["deal"].disabled = true; document.forms["controls"].elements["increase"].disabled = true; document.forms["controls"].elements["decrease"].disabled = true; DisablePlayButtons(); // If the burn card was reached, start a new deck. if (deck.cardCount() < burnCard) { alert("New deck."); newDeck(); } ...The DisablePlayButtons() function simply disables the "Split,""Double," "Surrender," "Hit" and "Stand" buttons. This must be done at severalother points in the code so it makes sense to define a function for it.
Next it takes the player's bet, deducting the amount from the player'scredits.
// Take the player's bet. player[0].bet = defaultBet; credits -= player[0].bet; updateBetDisplay(0);
The final step is to start dealing the initial cards for the player and thedealer. We could just call the .addCard() method twice on eachhand. But then all the cards would appear on the page at once. It's moredesirable to have a short pause before each card is dealt.
JavaScript has no function for pausing execution. Performing a busy wait,say with an empty for loop between each deal of a card, wouldn'thelp either. The browser will not update the display while script code isexecuting. A busy wait would just lock up the browser for a time, then all thecards would appear at once.
Instead, we create a function to deal one card at a time. To cause a delaybetween each deal of a card, the built-in setTimeout() functionwill be used. To start things off, the global variabledealRoundCounter is set to one and dealRound() iscalled.
// Start dealing the cards. dealRoundCounter = 1; dealRound();
Dealing the Cards
Within dealRound() a card is dealt according to the value ofdealRoundCounter. The first to the player, the second to thedealer, etc.
function dealRound(){ // Deal a card to the player or the dealer based on the counter. switch(dealRoundCounter) { case 1: player[0].addCard(getNextCard(), false); break; case 2: dealer.addCard(getNextCard(), true); break; case 3: player[0].addCard(getNextCard(), false); break; case 4: dealer.addCard(getNextCard(), false); break; default: // No more cards to deal, play the round. playRound(); return; break; } // Update the player's score. if (player[0].getScore() == 21) { player[0].blackjack = true; player[0].scoreTextNode.nodeValue = "Blackjack"; } else player[0].scoreTextNode.nodeValue = player[0].getScore(); // Set a timer for the next call. dealRoundCounter++; setTimeout(dealRound, dealTimeDelay);}Once a card is dealt, the player's score is updated, the counter isincremented, setTimeout() is called to fire another call todealRound (after a delay determined by dealTimeDelay)and the function exits.
By ending code execution, the browser is free to update the page, showingthe new card. When the timer expires, dealRound will execute againto deal the next card. After all the card have been dealt, theplayRound() function is called and we exit without setting atimer.
Evaluating the Initial Hands
The playRound() function examines the initial cards dealt tothe player and the dealer to determine what action to take.
First, if the dealer's face up card is an Ace, we need to offer the playerinsurance. As insurance is a side bet, the outcome doesn't affect the rest ofthe game play so a call is made to doInsurance() to handle this(see below) before moving on.
function playRound() { // If dealer's up card is an ace, offer insurance. if (dealer.cards[1].rank == "A") offerInsurance();If either the player or the dealer has a blackjack, the round is over.The function checks and will call endRound() to finish the roundand exit (step 5).
// Check for dealer blackjack. if (dealer.getScore() == 21) { dealer.blackjack = true; dealer.scoreTextNode.nodeValue = "Blackjack"; } // If player or dealer has blackjack, end the round. if (player[0].blackjack || dealer.blackjack) { endRound(); return; }If neither has blackjack, we move on and enable the play buttons: "Split"(if the player was dealt a pair), "Double," "Surrender," "Hit" and "Stand."The player's hand is highlighted and the function exits, leaving the game atstep 2, where the next action will depend on which button the playerpresses.
// Enable/disable buttons. if (canSplit()) document.forms["controls"].elements["split"].disabled = false; document.forms["controls"].elements["double"].disabled = false; document.forms["controls"].elements["surrender"].disabled = false; document.forms["controls"].elements["hit"].disabled = false; document.forms["controls"].elements["stand"].disabled = false; // Highlight the player's hand. addClassName(player[0].fieldNode, "activeField");}
Insurance
The doInsurance() function will prompt the player using thebuilt-in confirm() function, so execution will halt until theplayer responds to the dialog box.
function offerInsurance() { var amount; // Offer insurance bet to player. This is a side bet so it's resolved // here. if (confirm("Do you want to buy insurance?")) { // Take half of player's current bet from credits. amount = player[0].bet / 2; credits -= amount; // If the dealer has blackjack, show the down card and pay player at // 2 to 1. if (dealer.getScore() == 21) { dealer.cardsNode.firstChild.firstChild.style.visibility = ""; credits += player[0].bet; alert("Dealer has Blackjack, you win " + formatDollar(player[0].bet)); } else alert("Dealer does not have Blackjack, you lose " + formatDollar(amount)); // Update credits. updateBetDisplay(0); }}If the player selects "OK" to buy insurance, it adjusts the player's creditsand checks the dealer's hand for a blackjack. If the dealer has blackjack, itupdates the player's credits again to pay off the bet. In any case, it returnsexecution to the calling function, playRound().
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