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| 1 | +--- |
| 2 | +layout: recipe |
| 3 | +title: AJAX Request Without jQuery |
| 4 | +chapter: AJAX |
| 5 | +--- |
| 6 | +## Problem |
| 7 | + |
| 8 | +You want to load data from your server via AJAX without using the jQuery library. |
| 9 | + |
| 10 | +## Solution |
| 11 | + |
| 12 | +You will use the native <a href="http://en.wikipedia.org/wiki/XMLHttpRequest" target="_blank">XMLHttpRequest</a> object. |
| 13 | + |
| 14 | +Begin by making sure the XMLHttpRequest object exsits. |
| 15 | + |
| 16 | +{% highlight coffeescript %} |
| 17 | +# XMLHttpRequest.coffee |
| 18 | + |
| 19 | +if (typeof @XMLHttpRequest == "undefined") |
| 20 | + console.log 'XMLHttpRequest is undefined' |
| 21 | + |
| 22 | + @XMLHttpRequest = -> |
| 23 | + try |
| 24 | + return new ActiveXObject("Msxml2.XMLHTTP.6.0") |
| 25 | + catch error |
| 26 | + try |
| 27 | + return new ActiveXObject("Msxml2.XMLHTTP.3.0") |
| 28 | + catch error |
| 29 | + try |
| 30 | + return new ActiveXObject("Microsoft.XMLHTTP") |
| 31 | + catch error |
| 32 | + throw new Error("This browser does not support XMLHttpRequest.") |
| 33 | +{% endhighlight %} |
| 34 | + |
| 35 | +We can also set up some status codes. |
| 36 | + |
| 37 | +{% highlight coffeescript %} |
| 38 | +READYSTATE_UNINITIALIZED = 0 |
| 39 | +READYSTATE_LOADING = 1 |
| 40 | +READYSTATE_LOADED = 2 |
| 41 | +READYSTATE_INTERACTIVE = 3 |
| 42 | +READYSTATE_COMPLETE = 4 |
| 43 | +{% endhighlight %} |
| 44 | + |
| 45 | +Let's set up a simple test HTML page with a button. |
| 46 | + |
| 47 | +{% highlight html %} |
| 48 | +<!DOCTYPE HTML> |
| 49 | +<html lang="en-US"> |
| 50 | +<head> |
| 51 | + <meta charset="UTF-8"> |
| 52 | + <title>XMLHttpRequest Tester</title> |
| 53 | +</head> |
| 54 | +<body> |
| 55 | + <h1>XMLHttpRequest Tester</h1> |
| 56 | + <button id="loadDataButton">Load Data</button> |
| 57 | + |
| 58 | + <script type="text/javascript" src="XMLHttpRequest.js"></script> |
| 59 | +</body> |
| 60 | +</html> |
| 61 | +{% endhighlight %} |
| 62 | + |
| 63 | +Let's finish our XMLHttpRequest.coffee by adding a 'click' event listener then create our XMLHttpRequest object. |
| 64 | + |
| 65 | +{% highlight coffeescript linenos %} |
| 66 | +loadDataFromServer = -> |
| 67 | + req = new XMLHttpRequest() |
| 68 | + |
| 69 | + req.addEventListener 'readystatechange', -> |
| 70 | + if req.readyState is READYSTATE_COMPLETE |
| 71 | + if req.status is 200 or req.status is 304 |
| 72 | + data = eval '(' + req.responseText + ')' |
| 73 | + console.log 'data message: ', data.message |
| 74 | + else |
| 75 | + console.log 'Error loading data...' |
| 76 | + |
| 77 | + req.open 'GET', 'data.json', false |
| 78 | + req.send() |
| 79 | + |
| 80 | +loadDataButton = document.getElementById 'loadDataButton' |
| 81 | +loadDataButton.addEventListener 'click', loadDataFromServer, false |
| 82 | +{% endhighlight %} |
| 83 | + |
| 84 | +## Discussion |
| 85 | + |
| 86 | +In the above code, we create a new XMLHttpRequest instance on line 2. Then, we add an event listener for the readystatechange event. This fires whenever the XMLHttpRequest readyState changes. |
| 87 | + |
| 88 | +In the event handler we check to see if the readyState = READYSTATE_COMPLETE (value of 4). Then, we check to see if the status is either 200 or 304, both values are success indicators. |
| 89 | + |
| 90 | +If the request was indeed successful, we eval the JSON returned from the server and assign it to a data variable. At this point, we can use the returned data in any way we need to. |
| 91 | + |
| 92 | +The last thing we need to do is actually make our request. |
| 93 | + |
| 94 | +Line 12 opens a 'GET' request to retreive the data.json file. |
| 95 | + |
| 96 | +Line 13 sends our request to the server. |
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