JavaScript error: $ is undefined

This error comes when the jQuery library was not referenced or not loaded at all or not loaded properly.

Solution:

Add script reference to the jQuery library in your html file: you can download it and add it into your project or reference it from CDN.
```
<head>
<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
<script src="MyJavaScript.js"></script>
</head>
```

The order of your referenced scripts is important: make sure to add the jQuery library before your scripts.
So if we have a JavaScript file called MyJavaScript.js with the following code in it:

$(document).ready(function () {
$("myButton").click(function (event) {
alert("Hello world!");
});
});

This will not work:

<head>
<script src="MyJavaScript.js"></script>
<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
</head>

This will work:

<head>
<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
<script src="MyJavaScript.js"></script>
</head>

JavaScript error: $ is undefined

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Published by FitGeekGirl