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    <p>Some comments detailing the contract of the <code>multiplyByTwo</code> function would be helpful here:</p> <pre><code>// multiplyByTwo // num num num (num -&gt; x) -&gt; x[] function multiplyByTwo(a, b, c, callback) { ... </code></pre> <p>This means that the function takes four arguments, and returns an array of <code>x</code>. <code>x</code> can be any type. The first three arguments are numbers. The fourth argument to the function is actually a function itself. This function takes a number, and returns an <code>x</code>. Again, <code>x</code> can be any type, but it is the same type throughout the contract.</p> <p>Inside the <code>multiplyByTwo</code> function, the callback function is called once for each of the other arguments. The result of each of these calls is added to an array, which is the return value of <code>multiplyByTwo</code>.</p> <p>The <code>arguments</code> variable is a special variable in javascript, which, inside the scope of a function, gives access to all of the arguments to that function, as an array.</p> <p>The callback function is bound to the name <code>callback</code> in the scope of the <code>multiplyByTwo</code> function. It can then be called as any other function, such as by appending parentheses and arguments. The anonymous function that you gave when you called <code>multiplyByTwo</code> can then be referenced by that name.</p> <p>So, in the example given, <code>multiplyByTwo</code> is called with four arguments: <code>1</code>, <code>2</code>, <code>3</code>, and an anonymous function. Inside the scope of the <code>multiplyByTwo</code> function, these arguments are bound to the variables <code>a</code>, <code>b</code>, <code>c</code>, and <code>callback</code>, respectively. These arguments can also be referenced through the special <code>arguments</code> array. In the example, both methods are used to reference the arguments. The first three are referenced using the <code>arguments</code> array inside a loop, and the fourth argument is referenced using its name, as in <code>callback(...)</code>.</p>
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    1. PObetter understanding of callback functions in javascript
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    1. COI understand how callback is used in the loop, but how does it work for the anonymous one. Do you call that one arguments[4](arguments[i])
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    2. COYou could call the function with `arguments[4](arguments[i])`, but you can also call it by the name `callback`, since you bound it to that name by naming the arguments (well, you named the first four arguments anyway).
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    3. COThe first one was an example with a function attached to a variable.The second part should execute the same way according to the book, but it diddn't gave an example how the anonymous function was being called?
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