How to iterate through document nodes in javascript

ar total_words=0;
        var words_missing=false;
        var items = [];
        var myPosts = document.getElementById("doc_list").getElementsByTagName("span");
        for (var i = 0; i < myPosts.length; i++) {
            //omitting undefined null check for brevity
            if (myPosts[i].id.lastIndexOf("doc_wc_", 0) === 0) {
                console.log("found "+myPosts[i].id);
                var wc_text=$("#"+myPosts[i].id).text();
                if(wc_text=='')
                {
                    words_missing=true;
                    break;
                }
                else
                {
                    var wsIndex=wc_text.indexOf(" ");
                    var word_count=parseInt(wc_text.substring(0,wsIndex));
                    console.log(myPosts[i].id+" word count is "+word_count);
                    total_words=total_words+word_count;

                }
            }
        }