Highlight text in an html document

highlight.js

function selected(){
    var sel = window.getSelection(),
        cnt = sel.rangeCount,
        ranges=[];
    for(var i = 0; i < sel.rangeCount; i++)
      ranges[i] = sel.getRangeAt(i);
    return ranges
}

function highlight(node,sels){
    var html = node.innerHTML;
    sels.forEach(function(sel){
        html = html.replace(new RegExp(sel,"g"),"<span class='highlight'>$&</span>")
    })
    node.innerHTML = html
}

highlight(document.getElementById("foo"),selected())