Apply HTML tags across spans of text using Javascript.

applyTagAt

function applyTagAt(text, start, end, startTag, endTag) {
    var text2 = "";

    var counter = 0;
    var intag = false;
    var inescape = false;
    var tagstarted = false;
    for (var i = 0; i < text.length; i++) {

        if (text.charAt(i) == '<') {
            intag = true;
            if (tagstarted) {
                text2 += endTag; //End our tag
                if (counter == end) {
                    tagstarted = false;
                }
            }
        }

        if (counter == start && intag == false && inescape == false) {
            text2 += startTag;
            tagstarted = true;
            text2 += text.charAt(i);
        } else if (counter == end && inescape == false && tagstarted == true) {
            text2 += endTag;
            tagstarted = false;
            text2 += text.charAt(i);
        } else {
            text2 += text.charAt(i);
        }

        if (intag == true && text.charAt(i) == '>') {
            intag = false;
            if (tagstarted) {
                text2 += startTag;
            }
        } else if (intag == false && text.charAt(i) == '&') {
            inescape=true;
        } else if (inescape == true && text.charAt(i) == ';') {
            inescape=false;
            counter++;
        } else if (intag == false && inescape == false) {
            counter++;
        }

    }

    // counter can be incremented at the end
    if (counter == end && intag == false && inescape == false && tagstarted == true) {
        text2 += endTag;
    }

    //replace all instances of <startTag,endTag> (<em></em>) with empty string
    var text3 = text2.replace(startTag+endTag, "");
    while (text3 != text2) {
        text2 = text3;
        text3 = text2.replace(startTag+endTag, "");
    }

    return text2;
}