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    <p>With the code you have provided <code>test</code> will still be in scope inside the callback. <code>xhr</code> will not be, other than <code>xhr.responseText</code> being passed in as <code>data</code>.</p> <p><strong>Updated from comment</strong>:</p> <p>Assuming your code looks something like this:</p> <pre><code>for (var test in testers) getFileContents("hello"+test+".js", function(data) { alert(test); }); } </code></pre> <p>As this script runs, <code>test</code> will be assigned the values of the keys in <code>testers</code> - <code>getFileContents</code> is called each time, which starts a request in the background. As the request finishes, it calls the callback. <code>test</code> is going to contain the <strong>FINAL VALUE</strong> from the loop, as that loop has already finished executing. </p> <p>There is a technique you can use called a closure that will fix this sort of problem. You can create a function that returns your callback function, creating a new scope you can hold onto your variables with:</p> <pre><code>for (var test in testers) { getFileContents("hello"+test+".js", (function(test) { // lets create a function who has a single argument "test" // inside this function test will refer to the functions argument return function(data) { // test still refers to the closure functions argument alert(test); }; })(test) // immediately call the closure with the current value of test ); } </code></pre> <p>This will basically create a new scope (along with our new function) that will "hold on" to the value of <code>test</code>. </p> <p>Another way of writing the same sort of thing:</p> <pre><code>for (var test in testers) { (function(test) { // lets create a function who has a single argument "test" // inside this function test will refer to the functions argument // not the var test from the loop above getFileContents("hello"+test+".js", function(data) { // test still refers to the closure functions argument alert(test); }); })(test); // immediately call the closure with the value of `test` from `testers` } </code></pre>
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    1. POHow to structure javascript callback so that function scope is maintained properly
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    1. COWhat if the first block of code is in another .js file, included using the <script> tag? Would it still work?
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    2. COYes. "Enclosing Function Scope" means that your callback function extends its scope from the function it is declared in (which has the `test` variable). If the variables are not declared inside of any function, they will be in the "global scope".
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    3. COFinal question: If `test` is changing value inside of a `for each` loop, how come the last value of `test` is the only value that is printed by the `alert(test);` code? And how do I fix it so that it prints the value of `test` that was set during the call to `getFileContents`?
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