Swap image src if screen width <= 699
<p>I have two images "image-big.jpg" and "image-small.jpg" I want to via javascript detect if screen width &lt;= 699 and change the SRC of my image with class="imageswap" from image-big.jpg to image-small.jpg.</p>

<p>So basically if they are on a portable device it will display the smaller image.</p>

<p>I am novice at best with javascsript and any help is gratefully appreciated!</p>
