Sunday, 11 May 2014

Using JavaScript To Create Buttons

I wanted to make a quick blog post on how I've used JavaScript to create the rollover effects for the buttons in my navigation. The very first button I tried to create for my website was the home button. This is because logically, it comes first (it's in the top left). If you remember from my previous post about my home button I've decided to go with the following style for it.
This required me to have a rollover effect applied, so that when a mouse hit the 'up' image it swapped to the over image. I was having a lot of trouble with it - an unexpected, discouraging amount of trouble considering it was the very first thing I attempted. That was until I saw the following video, shared with me by a friend.
I followed this video to a tee, and it worked.

Following this video has given me a better understanding of how I can use JavaScript as before I'd never used it and never really understood what it was for. I've learnt how I can put code into the <head> of the document as a <script> which can then be referenced in the <body>. This is the code that I put into the <head> of my websites HTML.

<head>
<script type="text/javascript">
<!-- Home Button -->

function imgOver(id) {
document.getElementById(id).src="./graphics/home_grey_over.png";
}
function imgOut(id) {
document.getElementById(id).src="./graphics/home_grey_up.png";
}

</script>
</head>

The only "issue" with this technique is that I have to think of a unique way of saying 'over' and 'out; each time I use it for a different button. You can see in the example above I have 'imgOver' and 'imgOut'. If I wanted to use this again for another button I'd have to copy and paste the code over, change the src images and use alternative words - like 'imgOn' and 'imgOff'.

The above code is what goes in the <head> section of my html. There is another part that must go in the <body> section:

<div class="one-third column">
<a href="index.html" onmouseover="imgOver('homeButton');" onmouseout="imgOut('homeButton');">
<img src="graphics/home_grey_up.png" width="85px" height="auto" alt="home" id="homeButton" /> 
</a>
</div>

There are certain parts of this code that I can explain to show how it links with the script in the <head> and creates a image swap link.

a href: the link that the button leads to. In this case it is a home button, so it's destination is 'index.html' - the name of the home page.
onmouseover="imgOver": the words 'onmouseover' are recognised as a command, with 'imgOver' being in the script in the <head>. When a mouse is over the image, the browser should refer to the 'imgOver' code in the <head> which tells it which image to display/swap to.
onmouseout="imgOut": when the mouse is not over/on the image, the browser should display the image that is referred to under the 'imgOut' command in the script.

All of this code has resulted in creating a home button that has a rollover/image swap effect that also works as a link. I'll be using this for every image button that I create.

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