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POWhat does (function() mean in this particular code segment?
 

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  1. POWhat does (function() mean in this particular code segment?
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    <p>I'm (re)learning Ajax from the Mozilla site on <a href="https://developer.mozilla.org/en/AJAX/Getting_Started" rel="nofollow">https://developer.mozilla.org/en/AJAX/Getting_Started</a>, and I'm faced with this segment of code:</p> <pre><code>(function () { var httpRequest; document.getElementById("ajaxButton").onclick = function () { makeRequest('test.html'); }; function makeRequest(url) { if (window.XMLHttpRequest) { // Mozilla, Safari, ... httpRequest = new XMLHttpRequest(); } else if (window.ActiveXObject) { // IE try { httpRequest = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { httpRequest = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {} } } if (!httpRequest) { alert('Giving up :( Cannot create an XMLHTTP instance'); return false; } httpRequest.onreadystatechange = alertContents; httpRequest.open('GET', url); httpRequest.send(); } function alertContents() { if (httpRequest.readyState === 4) { if (httpRequest.status === 200) { alert(httpRequest.responseText); } else { alert('There was a problem with the request.'); } } } } //missing closing bracket added by bwalton 5/11/11. )(); </code></pre> <p>While I managed to understand the code and get it working, it's not until I stripped off the "(function() {" part at the top and all the end braces at the end of this code segment. The thing is I don't understand the purpose of" (function{", and it seems neither does FF. (It doesn't recognize this segment as Javascript until I stripped off the "(function{" portions. Does anyone know the purpose of this segment of code? I knew I've seen it somewhere as well, and this time I want to know exactly what it means. </p> <p>Thanks in advance for your help. </p>
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