<span class="kwd">var</span><span class="pln"> iterifyArr </span><span class="pun">=</span> <span class="kwd">function</span> <span class="pun">(</span><span class="pln">arr</span><span class="pun">)</span> <span class="pun">{</span>
<span class="kwd">var</span><span class="pln"> cur </span><span class="pun">=</span> <span class="lit">0</span><span class="pun">;</span><span class="pln">
arr</span><span class="pun">.</span><span class="kwd">next</span> <span class="pun">=</span> <span class="pun">(</span><span class="kwd">function</span> <span class="pun">()</span> <span class="pun">{</span> <span class="kwd">return</span> <span class="pun">(++</span><span class="pln">cur </span><span class="pun">>=</span> <span class="kwd">this</span><span class="pun">.</span><span class="pln">length</span><span class="pun">)</span> <span class="pun">?</span> <span class="kwd">false</span> <span class="pun">:</span> <span class="kwd">this</span><span class="pun">[</span><span class="pln">cur</span><span class="pun">];</span> <span class="pun">});</span><span class="pln">
arr</span><span class="pun">.</span><span class="pln">prev </span><span class="pun">=</span> <span class="pun">(</span><span class="kwd">function</span> <span class="pun">()</span> <span class="pun">{</span> <span class="kwd">return</span> <span class="pun">(--</span><span class="pln">cur </span><span class="pun"><</span> <span class="lit">0</span><span class="pun">)</span> <span class="pun">?</span> <span class="kwd">false</span> <span class="pun">:</span> <span class="kwd">this</span><span class="pun">[</span><span class="pln">cur</span><span class="pun">];</span> <span class="pun">});</span>
<span class="kwd">return</span><span class="pln"> arr</span><span class="pun">;</span>
<span class="pun">};</span>
<span class="kwd">var</span><span class="pln"> fibonacci </span><span class="pun">=</span> <span class="pun">[</span><span class="lit">1</span><span class="pun">,</span> <span class="lit">1</span><span class="pun">,</span> <span class="lit">2</span><span class="pun">,</span> <span class="lit">3</span><span class="pun">,</span> <span class="lit">5</span><span class="pun">,</span> <span class="lit">8</span><span class="pun">,</span> <span class="lit">13</span><span class="pun">];</span><span class="pln">
iterifyArr</span><span class="pun">(</span><span class="pln">fibonacci</span><span class="pun">);</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="pln">prev</span><span class="pun">();</span> <span class="com">// returns false</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 1</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 1</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 2</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 3</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 5</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 8</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="pln">prev</span><span class="pun">();</span> <span class="com">// returns 5</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 8</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns 13</span><span class="pln">
fibonacci</span><span class="pun">.</span><span class="kwd">next</span><span class="pun">();</span> <span class="com">// returns false</span>