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    <p>1.</p> <p>The return value of <code>||</code> is not boolean.</p> <p>It is the first argument if it is truthy or the second argument if it is not.</p> <p>So <code>a || b</code> is equivalent to <code>a ? a : b</code> and <code>a &amp;&amp; b</code> is equivalent to <code>a ? b : a</code>.</p> <p>2.</p> <p>When power is called, a new frame is pushed onto the call stack to hold the paramaters and local variables like other languages. But JavaScript is a bit different from many languages in that when a function call results in a new function instance being created, the new function instance holds a reference to the stack frames on the stack when it is created. Since these stack frames hold locals, there is a different place in memory for functions created by different calls to the same function.</p> <p>For example, in</p> <pre><code>function makeCounter() { var counter = 0; return function () { return counter++; }; } var c1 = makeCounter(); var c2 = makeCounter(); c1(); c1(); c1(); c2(); c2(); alert(c1() + ", " + c2()); // -&gt; 3, 2 alert(c1() + ", " + c2()); // -&gt; 4, 3 </code></pre> <p><code>makeCounter</code> is first called to initialize <code>c1</code>. This creates a stack frame like <code>{ counter: 0 }</code> which the first counter function points to. The second call to <code>makeCounter</code> used to initialize <code>c2</code> creates a different stack frame.</p> <p>So the code above is equivalent to</p> <pre><code>var c1SFrame = { counter: 0 }; var c2SFrame = { counter: 0 }; c1SFrame.counter++; c1SFrame.counter++; c1SFrame.counter++; c2SFrame.counter++; c2SFrame.counter++; c2SFrame.counter++; alert(c1SFrame++ + ", " + c2SFrame++); alert(c1SFrame++ + ", " + c2SFrame++); </code></pre> <p>which should make it obvious why it alerts what it does.</p>
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    1. USMike Samuel
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    1. COIf x=10 and y= 5 then (x=10) || (y=10) return is true .this example is like the above example. why the above return value is not boolean.
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      1. USzhuanzhou
    2. CO@zhuanzhou, no, the result of `(x=10) || (y=10)` is `10` since the result of both assignments is `10`. If you meant to say, `(x == 10) || (y == 10)` then that would be true because the result of `x == 10` is `true` and `true ? true : false` is `true`.
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      1. USMike Samuel
    3. COi found the example form this.http://bton.com/tb16/jsref/operator.html (Comparison and Logical Operators part)so the examplt is wrong? am i right? thank you.
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