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copied!<p>The code is equivalent to the following:</p> <pre><code>var cc; cc = cc || {}; cc = cc; </code></pre> <p>which obviously is a mistake.</p> <p><strong>UPDATE.</strong> I did more research on this topic and here's an interesting thing:</p> <p>Whenever you use <code>var</code> keyword it creates a new variable in current scope unless it already exists <strong>in current scope</strong>. Basically this code:</p> <pre><code>var cc = 1; function test() { var cc = cc || {}; return cc; } test(); </code></pre> <p>will always produce <code>{}</code>, no matter what the initial value of <code>cc</code> ( in global scope ) is. In particular this code:</p> <pre><code>var cc = [expression]; </code></pre> <p>is equivalent to:</p> <pre><code>var cc; cc = [expression]; </code></pre> <p>although <code>var cc;</code> creates new variable <strong>only if</strong> <code>cc</code> does not exist in current scope.</p> <p><strong>UPDATE 2.</strong> What operation takes precedence is confusing because in OP's code both <code>=</code> signs actually are not the same. The first one denotes variable declaration, because there is a <code>var</code> keyword before it. The second one is an assignment. That's why</p> <pre><code>var x = y = z; </code></pre> <p>is equivalent to</p> <pre><code>var x; y = z; x = z; </code></pre> <p>( note that <code>var</code> keyword applies only to <code>x</code> ) while</p> <pre><code>x = y = z; </code></pre> <p>is equivalent to</p> <pre><code>y = z; x = z; </code></pre> <p>( note that operation <code>y=z</code> returns <code>z</code>, which doesn't really matter (it could be <code>y</code> obviously) but it is worth noting )</p> <p><strong>CONCLUSION:</strong> Variable declaration on the left side <strong>always</strong> comes before evaluation of the right side and assignment of the right side to the left side.</p>

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