<img alt="" class="..." style="..." src="/image.jpg">
<img alt="" class="..." style="..." src="/image.jpg">
<img alt="" class="..." style="..." src="/image.jpg">
<img alt="" class="..." style="..." src="/image.jpg">
<img alt="" class="..." style="..." src="/image.jpg">

var container = document.getElementById('content'),
    elements = container.getElementsByTagName('img');
[].forEach.call(elements, function( el ) {
    el.removeAttribute('class');
    el.removeAttribute('style');
});