This should work:
var link = document.querySelector('#arrow a');
link.onclick = function() {
var image = document.querySelector('#arrow a img');
if(this.href.slice(-1) === '1') {
this.href = '#DIV2';
image.src = 'https://cdn1.iconfinder.com/data/icons/nuvola2/48x48/actions/1uparrow.png';
} else {
this.href = '#DIV1';
image.src = 'https://cdn1.iconfinder.com/data/icons/nuvola2/48x48/actions/1downarrow.png';
}
}
See it in action here: http://jsfiddle.net/TM9ap/7/
Note that I've changed the href
attribute in the link to #DIV1
like this <a href="#DIV1">