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<h1 class="title">pong.js Example File</h1>
<span class="small-subtitle">script/context2d/scripts/pong.js</span>
<!-- $$$script/context2d/scripts/pong.js-description -->
<div class="descr"> <a name="details"></a>
<pre class="js"> <span class="comment">// globals</span>
<span class="name">playarea_canvas</span> <span class="operator">=</span> <span class="name">document</span>.<span class="name">getElementById</span>(<span class="string">'tutorial'</span>);
<span class="name">playarea_canvas</span>.<span class="name">resize</span>(<span class="number">320</span>,<span class="number">200</span>);
<span class="name">playarea</span> <span class="operator">=</span> <span class="name">playarea_canvas</span>.<span class="name">getContext</span>(<span class="string">'2d'</span>);
<span class="comment">//p1_scr = document.getElementById('p1_scr');</span>
<span class="comment">//p2_scr = document.getElementById('p2_scr');</span>
<span class="comment">//status_msg = document.getElementById('status');</span>
<span class="comment">//debug = document.getElementById('debug');</span>
<span class="name">ball_direction</span> <span class="operator">=</span> <span class="number">0</span>;
<span class="name">up</span> <span class="operator">=</span> -<span class="number">1</span>;
<span class="name">down</span> <span class="operator">=</span> <span class="number">1</span>;
<span class="comment">//key codes</span>
<span class="name">key_up</span> <span class="operator">=</span> <span class="number">38</span>;
<span class="name">key_down</span> <span class="operator">=</span> <span class="number">40</span>;
<span class="name">key_W</span> <span class="operator">=</span> <span class="number">87</span>;
<span class="name">key_S</span> <span class="operator">=</span> <span class="number">83</span>;
<span class="name">key_pause</span> <span class="operator">=</span> <span class="number">32</span>;
<span class="name">speed</span> <span class="operator">=</span> <span class="number">2</span>; <span class="comment">//controls the speed of the ball</span>
<span class="name">paddle_inc</span> <span class="operator">=</span> <span class="number">10</span>; <span class="comment">//how many pixels paddle can move in either direction</span>
<span class="name">pause</span> <span class="operator">=</span> <span class="number">false</span>;
<span class="name">player_1</span> <span class="operator">=</span> <span class="number">0</span>; <span class="comment">//player IDs</span>
<span class="name">player_2</span> <span class="operator">=</span> <span class="number">1</span>;
<span class="name">player_1_scr</span> <span class="operator">=</span> <span class="number">0</span>; <span class="comment">//player scores</span>
<span class="name">player_2_scr</span> <span class="operator">=</span> <span class="number">0</span>;
<span class="name">player_1_direction</span> <span class="operator">=</span> <span class="number">null</span>; <span class="comment">//null = no movement whatsoever</span>
<span class="name">player_2_direction</span> <span class="operator">=</span> <span class="number">null</span>;
<span class="name">pa</span> <span class="operator">=</span> new <span class="name">Array</span>();
<span class="name">divider</span> <span class="operator">=</span> new <span class="name">Array</span>();
<span class="name">paddle_1</span> <span class="operator">=</span> new <span class="name">Array</span>();
<span class="name">paddle_2</span> <span class="operator">=</span> new <span class="name">Array</span>();
<span class="name">ball</span> <span class="operator">=</span> new <span class="name">Array</span>();
<span class="keyword">function</span> <span class="name">sleep</span>(<span class="name">numberMillis</span>)
{
var <span class="name">now</span> = new <span class="name">Date</span>();
var <span class="name">exitTime</span> = <span class="name">now</span>.<span class="name">getTime</span>() <span class="operator">+</span> <span class="name">numberMillis</span>;
<span class="keyword">while</span> (<span class="number">true</span>) {
<span class="name">now</span> <span class="operator">=</span> new <span class="name">Date</span>();
<span class="keyword">if</span> (<span class="name">now</span>.<span class="name">getTime</span>() <span class="operator">></span> <span class="name">exitTime</span>)
<span class="keyword">return</span>;
}
}
<span class="keyword">function</span> <span class="name">init</span>()
{
<span class="name">pa</span>[<span class="string">'width'</span>] <span class="operator">=</span> <span class="number">150</span>;
<span class="name">pa</span>[<span class="string">'height'</span>] <span class="operator">=</span> <span class="number">140</span>;
<span class="name">pa</span>[<span class="string">'player_margin'</span>] <span class="operator">=</span> <span class="number">10</span>; <span class="comment">//area behind player paddles</span>
<span class="name">pa</span>[<span class="string">'foreground'</span>] <span class="operator">=</span> <span class="string">"#FFFFFF"</span>;
<span class="name">pa</span>[<span class="string">'background'</span>] <span class="operator">=</span> <span class="string">"#000000"</span>;
<span class="name">divider</span>[<span class="string">'pos'</span>] <span class="operator">=</span> <span class="name">pa</span>[<span class="string">'width'</span>]<span class="operator">/</span><span class="number">2</span>;
<span class="name">divider</span>[<span class="string">'width'</span>] <span class="operator">=</span> <span class="number">4</span>;
<span class="name">paddle_1</span>[<span class="string">'width'</span>] <span class="operator">=</span> <span class="number">8</span>;
<span class="name">paddle_1</span>[<span class="string">'height'</span>] <span class="operator">=</span> <span class="number">64</span>;
<span class="name">paddle_1</span>[<span class="string">'x'</span>] <span class="operator">=</span> <span class="name">pa</span>[<span class="string">'player_margin'</span>];
<span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator">=</span> (<span class="name">pa</span>[<span class="string">'height'</span>] <span class="operator">/</span><span class="number">2</span> ) <span class="operator">-</span> (<span class="name">paddle_1</span>[<span class="string">'height'</span>] <span class="operator">/</span> <span class="number">2</span>);
<span class="name">paddle_2</span>[<span class="string">'width'</span>] <span class="operator">=</span> <span class="number">8</span>;
<span class="name">paddle_2</span>[<span class="string">'height'</span>] <span class="operator">=</span> <span class="number">64</span>;
<span class="name">paddle_2</span>[<span class="string">'x'</span>] <span class="operator">=</span> (<span class="name">pa</span>[<span class="string">'width'</span>] <span class="operator">-</span> <span class="name">pa</span>[<span class="string">'player_margin'</span>] <span class="operator">-</span> <span class="name">paddle_2</span>[<span class="string">'width'</span>]);
<span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator">=</span> (<span class="name">pa</span>[<span class="string">'height'</span>] <span class="operator">/</span><span class="number">2</span> ) <span class="operator">-</span> (<span class="name">paddle_2</span>[<span class="string">'height'</span>] <span class="operator">/</span> <span class="number">2</span>);
<span class="name">ball</span>[<span class="string">'width'</span>] <span class="operator">=</span> <span class="number">10</span>;
<span class="name">ball</span>[<span class="string">'height'</span>] <span class="operator">=</span> <span class="number">10</span>;
<span class="name">ball</span>[<span class="string">'x'</span>] <span class="operator">=</span> (<span class="name">pa</span>[<span class="string">'width'</span>]<span class="operator">/</span><span class="number">2</span>) <span class="operator">-</span> (<span class="name">ball</span>[<span class="string">'width'</span>] <span class="operator">/</span> <span class="number">2</span>);
<span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator">=</span> (<span class="name">pa</span>[<span class="string">'height'</span>]<span class="operator">/</span><span class="number">2</span>) <span class="operator">-</span> (<span class="name">ball</span>[<span class="string">'height'</span>] <span class="operator">/</span> <span class="number">2</span>);
<span class="name">ball_direction</span> <span class="operator">=</span> <span class="name">Math</span>.<span class="name">random</span>() <span class="operator">*</span> <span class="number">360</span>; <span class="comment">//initialize ball direction, which is determined by angle, at random</span>
<span class="name">speed</span> <span class="operator">=</span> <span class="number">2</span>;
}
<span class="keyword">function</span> <span class="name">renderPlayarea</span>()
{
<span class="name">playarea</span>.<span class="name">beginPath</span>();
<span class="name">playarea</span>.<span class="name">clearRect</span>(<span class="number">0</span>,<span class="number">0</span>,<span class="name">pa</span>[<span class="string">'width'</span>],<span class="name">pa</span>[<span class="string">'height'</span>]);
<span class="name">playarea</span>.<span class="name">fillStyle</span> <span class="operator">=</span> <span class="name">pa</span>[<span class="string">'background'</span>];
<span class="name">playarea</span>.<span class="name">strokeStyle</span> <span class="operator">=</span> <span class="name">pa</span>[<span class="string">'foreground'</span>];
<span class="name">playarea</span>.<span class="name">fillRect</span>(<span class="number">0</span>,<span class="number">0</span>, <span class="name">pa</span>[<span class="string">'width'</span>], <span class="name">pa</span>[<span class="string">'height'</span>]);
<span class="comment">//move paddles</span>
<span class="keyword">if</span>(<span class="name">player_1_direction</span> <span class="operator">!=</span> <span class="number">null</span>)
{
<span class="keyword">if</span>(<span class="name">player_1_direction</span> <span class="operator">==</span> <span class="name">up</span>)
<span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator">=</span> <span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator">-</span> <span class="name">paddle_inc</span>;
else
<span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator">=</span> <span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator">+</span> <span class="name">paddle_inc</span>;
}
<span class="keyword">if</span>(<span class="name">player_2_direction</span> <span class="operator">!=</span> <span class="number">null</span>)
{
<span class="keyword">if</span>(<span class="name">player_2_direction</span> <span class="operator">==</span> <span class="name">up</span>)
<span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator">=</span> <span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator">-</span> <span class="name">paddle_inc</span>;
else
<span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator">=</span> <span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator">+</span> <span class="name">paddle_inc</span>;
}
<span class="name">playarea</span>.<span class="name">rect</span>(<span class="name">paddle_1</span>[<span class="string">'x'</span>],<span class="name">paddle_1</span>[<span class="string">'y'</span>],<span class="name">paddle_1</span>[<span class="string">'width'</span>],<span class="name">paddle_1</span>[<span class="string">'height'</span>]);
<span class="name">playarea</span>.<span class="name">rect</span>(<span class="name">paddle_2</span>[<span class="string">'x'</span>],<span class="name">paddle_2</span>[<span class="string">'y'</span>],<span class="name">paddle_2</span>[<span class="string">'width'</span>],<span class="name">paddle_2</span>[<span class="string">'height'</span>]);
<span class="comment">//move ball</span>
<span class="name">playarea</span>.<span class="name">rect</span>(<span class="name">ball</span>[<span class="string">'x'</span>], <span class="name">ball</span>[<span class="string">'y'</span>], <span class="name">ball</span>[<span class="string">'width'</span>], <span class="name">ball</span>[<span class="string">'height'</span>]);
<span class="name">ball</span>[<span class="string">'x'</span>] <span class="operator">=</span> <span class="name">ball</span>[<span class="string">'x'</span>] <span class="operator">+</span> <span class="name">Math</span>.<span class="name">cos</span>((<span class="name">ball_direction</span>)<span class="operator">*</span><span class="name">Math</span>.<span class="name">PI</span><span class="operator">/</span><span class="number">180</span>) <span class="operator">*</span> <span class="name">speed</span>;
<span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator">=</span> <span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator">+</span> <span class="name">Math</span>.<span class="name">sin</span>((<span class="name">ball_direction</span>)<span class="operator">*</span><span class="name">Math</span>.<span class="name">PI</span><span class="operator">/</span><span class="number">180</span>) <span class="operator">*</span> <span class="name">speed</span>;
<span class="name">playarea</span>.<span class="name">fillStyle</span> <span class="operator">=</span> <span class="name">pa</span>[<span class="string">'foreground'</span>];
<span class="name">playarea</span>.<span class="name">fill</span>();
<span class="name">playarea</span>.<span class="name">beginPath</span>();
<span class="comment">//redraw divider</span>
<span class="name">playarea</span>.<span class="name">lineWidth</span> <span class="operator">=</span> <span class="name">divider</span>[<span class="string">'width'</span>];
<span class="name">playarea</span>.<span class="name">lineTo</span>(<span class="name">divider</span>[<span class="string">'pos'</span>], <span class="number">0</span>);
<span class="name">playarea</span>.<span class="name">lineTo</span>(<span class="name">divider</span>[<span class="string">'pos'</span>], <span class="name">pa</span>[<span class="string">'height'</span>] <span class="operator">=</span> <span class="number">200</span>);
<span class="name">playarea</span>.<span class="name">lineWidth</span> <span class="operator">=</span> <span class="number">1</span>;
<span class="name">playarea</span>.<span class="name">stroke</span>();
<span class="name">playarea</span>.<span class="name">closePath</span>();
}
<span class="keyword">function</span> <span class="name">testCollisions</span>()
{
<span class="comment">//make sure paddles don't go beyond play area</span>
<span class="keyword">if</span>(((<span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator"><=</span> <span class="number">0</span>) <span class="operator">&&</span> (<span class="name">player_1_direction</span> <span class="operator">==</span> <span class="name">up</span>)) <span class="operator">||</span> ((<span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator">>=</span> (<span class="name">pa</span>[<span class="string">'height'</span>] <span class="operator">-</span> <span class="name">paddle_1</span>[<span class="string">'height'</span>])) <span class="operator">&&</span> (<span class="name">player_1_direction</span> <span class="operator">==</span> <span class="name">down</span>)))
<span class="name">player_1_direction</span> <span class="operator">=</span> <span class="number">null</span>;
<span class="keyword">if</span>(((<span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator"><=</span> <span class="number">0</span>) <span class="operator">&&</span> (<span class="name">player_2_direction</span> <span class="operator">==</span> <span class="name">up</span>)) <span class="operator">||</span> ((<span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator">>=</span> (<span class="name">pa</span>[<span class="string">'height'</span>] <span class="operator">-</span> <span class="name">paddle_2</span>[<span class="string">'height'</span>])) <span class="operator">&&</span> (<span class="name">player_2_direction</span> <span class="operator">==</span> <span class="name">down</span>)))
<span class="name">player_2_direction</span> <span class="operator">=</span> <span class="number">null</span>;
<span class="comment">//check to see if ball went beyond paddles, and if so, score accordingly and reset playarea</span>
<span class="keyword">if</span>(<span class="name">ball</span>[<span class="string">'x'</span>] <span class="operator"><=</span> <span class="number">0</span>)
{
<span class="name">setScore</span>(<span class="name">player_2</span>);
<span class="name">init</span>()
<span class="name">sleep</span>(<span class="number">1000</span>);
}
<span class="keyword">if</span>(<span class="name">ball</span>[<span class="string">'x'</span>] <span class="operator">>=</span> (<span class="name">pa</span>[<span class="string">'width'</span>] <span class="operator">-</span> <span class="name">ball</span>[<span class="string">'width'</span>]))
{
<span class="name">setScore</span>(<span class="name">player_1</span>);
<span class="name">init</span>();
<span class="name">sleep</span>(<span class="number">1000</span>);
}
<span class="comment">//check to see if ball hit top or bottom wall. if so, change direction</span>
<span class="keyword">if</span>((<span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator">>=</span> (<span class="name">pa</span>[<span class="string">'height'</span>] <span class="operator">-</span> <span class="name">ball</span>[<span class="string">'height'</span>])) <span class="operator">||</span> <span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator"><=</span> <span class="number">0</span>)
<span class="name">ball_direction</span> <span class="operator">=</span> -<span class="name">ball_direction</span>;
<span class="comment">//check to see if the ball hit a paddle, and if so, change ball angle dependant on where it hit the paddle</span>
<span class="keyword">if</span>((<span class="name">ball</span>[<span class="string">'x'</span>] <span class="operator"><=</span> (<span class="name">paddle_1</span>[<span class="string">'x'</span>] <span class="operator">+</span> <span class="name">paddle_1</span>[<span class="string">'width'</span>])) <span class="operator">&&</span> (<span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator">>=</span> <span class="name">paddle_1</span>[<span class="string">'y'</span>]) <span class="operator">&&</span> (<span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator"><=</span> (<span class="name">paddle_1</span>[<span class="string">'y'</span>] <span class="operator">+</span> <span class="name">paddle_1</span>[<span class="string">'height'</span>])))
{
<span class="name">ball_direction</span> <span class="operator">=</span> -<span class="name">ball_direction</span><span class="operator">/</span><span class="number">2</span>;
<span class="name">speed</span> <span class="operator">+=</span> <span class="number">.5</span>;
}
<span class="keyword">if</span>(((<span class="name">ball</span>[<span class="string">'x'</span>] <span class="operator">+</span> <span class="name">ball</span>[<span class="string">'width'</span>]) <span class="operator">>=</span> <span class="name">paddle_2</span>[<span class="string">'x'</span>]) <span class="operator">&&</span> (<span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator">>=</span> <span class="name">paddle_2</span>[<span class="string">'y'</span>]) <span class="operator">&&</span> (<span class="name">ball</span>[<span class="string">'y'</span>] <span class="operator"><=</span> (<span class="name">paddle_2</span>[<span class="string">'y'</span>] <span class="operator">+</span> <span class="name">paddle_2</span>[<span class="string">'height'</span>])))
{
<span class="name">ball_direction</span> <span class="operator">=</span> (<span class="number">180</span><span class="operator">+</span><span class="name">ball_direction</span>)<span class="operator">/</span><span class="number">2</span>;
<span class="name">speed</span> <span class="operator">+=</span> <span class="number">.5</span>;
}
}
<span class="keyword">function</span> <span class="name">setScore</span>(<span class="name">p</span>)
{
<span class="keyword">if</span>(<span class="name">p</span> <span class="operator">==</span> <span class="name">player_1</span>)
{
player_1_scr++;
<span class="comment">//p1_scr.firstChild.nodeValue = player_1_scr;</span>
}
<span class="keyword">if</span>(<span class="name">p</span> <span class="operator">==</span> <span class="name">player_2</span>)
{
player_2_scr++;
<span class="comment">//p2_scr.firstChild.nodeValue = player_2_scr;</span>
}
}
<span class="comment">//handle input</span>
<span class="name">document</span>.<span class="name">onkeydown</span> <span class="operator">=</span> <span class="keyword">function</span>(<span class="name">ev</span>)
{
<span class="keyword">switch</span>(<span class="name">ev</span>.<span class="name">keyCode</span>)
{
<span class="keyword">case</span> <span class="name">key_W</span>:
<span class="name">player_1_direction</span> <span class="operator">=</span> <span class="name">up</span>;
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="name">key_S</span>:
<span class="name">player_1_direction</span> <span class="operator">=</span> <span class="name">down</span>;
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="name">key_up</span>:
<span class="name">player_2_direction</span> <span class="operator">=</span> <span class="name">up</span>;
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="name">key_down</span>:
<span class="name">player_2_direction</span> <span class="operator">=</span> <span class="name">down</span>;
<span class="keyword">break</span>;
}
}
<span class="name">document</span>.<span class="name">onkeyup</span> <span class="operator">=</span> <span class="keyword">function</span>(<span class="name">ev</span>)
{
<span class="keyword">switch</span>(<span class="name">ev</span>.<span class="name">keyCode</span>)
{
<span class="keyword">case</span> <span class="name">key_W</span>:
<span class="keyword">case</span> <span class="name">key_S</span>:
<span class="name">player_1_direction</span> <span class="operator">=</span> <span class="number">null</span>;
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="name">key_up</span>:
<span class="keyword">case</span> <span class="name">key_down</span>:
<span class="name">player_2_direction</span> <span class="operator">=</span> <span class="number">null</span>;
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="name">key_pause</span>:
<span class="keyword">if</span>(<span class="name">pause</span> <span class="operator">==</span> <span class="number">false</span>)
{
<span class="name">clearInterval</span>(<span class="name">game</span>);
<span class="comment">//status_msg.style.visibility = "visible";</span>
<span class="name">pause</span> <span class="operator">=</span> <span class="number">true</span>;
}
else
{
<span class="name">game</span> <span class="operator">=</span> <span class="name">setInterval</span>(<span class="name">main</span>, <span class="number">25</span>);
<span class="comment">//status_msg.style.visibility = "hidden";</span>
<span class="name">pause</span> <span class="operator">=</span> <span class="number">false</span>;
}
<span class="keyword">break</span>;
}
}
<span class="keyword">function</span> <span class="name">main</span>()
{
<span class="name">testCollisions</span>();
<span class="name">renderPlayarea</span>();
}
<span class="name">init</span>();
<span class="name">game</span> <span class="operator">=</span> <span class="name">setInterval</span>(<span class="name">main</span>, <span class="number">25</span>);</pre>
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