function init_buttons() {
    var allHTMLTags=document.getElementsByTagName("*");
    
    for (i=0; i<allHTMLTags.length; i++) {
        var classes = allHTMLTags[i].className.split(" ");
       
        if (classes[0]=="sellfy-buy-button") {
            var href =allHTMLTags[i].getAttribute('href')
            var url = href.substring(0,href.indexOf("/p/")+1);
            var id = allHTMLTags[i].id;
            var iframe_dimensions = "";
            if ( classes[1] == "sellfy-large" ) {
                iframe_dimensions = 'width:76px; height:79px; overflow:hidden;';
            } else {
                iframe_dimensions = 'width:140px; height:25px;';
            }
            allHTMLTags[i].innerHTML='<iframe style="'+iframe_dimensions+'" src="'+url+'buttons/'+id+'/'+classes[1]+'" allowtransparency="true" frameborder="0" scrolling="no"/>';
        }    
    }
} 
window.onload = init_buttons;