diff --git a/asn1.js b/asn1.js
index d157950..5dde9a3 100644
--- a/asn1.js
+++ b/asn1.js
@@ -348,6 +348,29 @@ function recurse(el, parser, maxLength) {
     return d;
 }
 
+class ASN1Tag {
+    constructor(stream) {
+        let buf = stream.get();
+        this.tagClass = buf >> 6;
+        this.tagConstructed = ((buf & 0x20) !== 0);
+        this.tagNumber = buf & 0x1F;
+        if (this.tagNumber == 0x1F) { // long tag
+            let n = new Int10();
+            do {
+                buf = stream.get();
+                n.mulAdd(128, buf & 0x7F);
+            } while (buf & 0x80);
+            this.tagNumber = n.simplify();
+        }
+    }
+    isUniversal() {
+        return this.tagClass === 0x00;
+    };
+    isEOC() {
+        return this.tagClass === 0x00 && this.tagNumber === 0x00;
+    };
+}
+
 class ASN1 {
     constructor(stream, header, length, tag, tagLen, sub) {
         if (!(tag instanceof ASN1Tag)) throw 'Invalid tag value.';
@@ -519,7 +542,9 @@ class ASN1 {
             buf = (buf * 256) + stream.get();
         return buf;
     };
-    static decode(stream, offset) {
+    static decode(stream, offset, type = ASN1) {
+        if (!(type.prototype instanceof ASN1))
+            throw 'Must pass a class that extends ASN1';
         if (!(stream instanceof Stream))
             stream = new Stream(stream, offset || 0);
         let streamStart = new Stream(stream),
@@ -537,14 +562,14 @@ class ASN1 {
                     if (end > stream.enc.length)
                         throw 'Container at offset ' + start +  ' has a length of ' + len + ', which is past the end of the stream';
                     while (stream.pos < end)
-                        sub[sub.length] = ASN1.decode(stream);
+                        sub[sub.length] = type.decode(stream);
                     if (stream.pos != end)
                         throw 'Content size is not correct for container at offset ' + start;
                 } else {
                     // undefined length
                     try {
                         for (;;) {
-                            let s = ASN1.decode(stream);
+                            let s = type.decode(stream);
                             if (s.tag.isEOC())
                                 break;
                             sub[sub.length] = s;
@@ -579,34 +604,11 @@ class ASN1 {
                 throw "We can't skip over an invalid tag with undefined length at offset " + start;
             stream.pos = start + Math.abs(len);
         }
-        return new ASN1(streamStart, header, len, tag, tagLen, sub);
+        return new type(streamStart, header, len, tag, tagLen, sub);
     };
 
 }
 
-class ASN1Tag {
-    constructor(stream) {
-        let buf = stream.get();
-        this.tagClass = buf >> 6;
-        this.tagConstructed = ((buf & 0x20) !== 0);
-        this.tagNumber = buf & 0x1F;
-        if (this.tagNumber == 0x1F) { // long tag
-            let n = new Int10();
-            do {
-                buf = stream.get();
-                n.mulAdd(128, buf & 0x7F);
-            } while (buf & 0x80);
-            this.tagNumber = n.simplify();
-        }
-    }
-    isUniversal() {
-        return this.tagClass === 0x00;
-    };
-    isEOC() {
-        return this.tagClass === 0x00 && this.tagNumber === 0x00;
-    };
-}
-
 return ASN1;
 
 });
diff --git a/dom.js b/dom.js
index 6a474c3..f293eb4 100644
--- a/dom.js
+++ b/dom.js
@@ -14,8 +14,8 @@
 // OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 (typeof define != 'undefined' ? define : function (factory) { 'use strict';
-    if (typeof module == 'object') factory(function (name) { return require(name); });
-    else factory(function (name) { return window[name.substring(2)]; });
+    if (typeof module == 'object') module.exports = factory(function (name) { return require(name); });
+    else window.dom = factory(function (name) { return window[name.substring(2)]; });
 })(function (require) {
 'use strict';
 
@@ -57,166 +57,175 @@ const
         }
     };
 
-ASN1.prototype.toDOM = function (spaces) {
-    spaces = spaces || '';
-    let isOID = (typeof oids === 'object') && (this.tag.isUniversal() && (this.tag.tagNumber == 0x06) || (this.tag.tagNumber == 0x0D));
-    let node = DOM.tag('div', 'node');
-    node.asn1 = this;
-    let head = DOM.tag('div', 'head');
-    head.innerHTML = "<span class='spaces'>" + spaces + '</span>' + this.typeName().replace(/_/g, ' ');
-    let content = this.content(contentLength);
-    let oid;
-    if (content !== null) {
-        let preview = DOM.tag('span', 'preview'),
-            shortContent;
-        if (isOID)
-            content = content.split('\n', 1)[0];
-        shortContent = (content.length > lineLength) ? content.substring(0, lineLength) + DOM.ellipsis : content;
-        preview.appendChild(DOM.space());
-        preview.appendChild(DOM.text(shortContent));
-        if (isOID) {
-            oid = oids[content];
-            if (oid) {
-                if (oid.d) {
-                    preview.appendChild(DOM.space());
-                    let oidd = DOM.tag('span', 'oid description');
-                    oidd.appendChild(DOM.text(oid.d));
-                    preview.appendChild(oidd);
-                }
-                if (oid.c) {
-                    preview.appendChild(DOM.space());
-                    let oidc = DOM.tag('span', 'oid comment');
-                    oidc.appendChild(DOM.text('(' + oid.c + ')'));
-                    preview.appendChild(oidc);
+class ASN1DOM extends ASN1 {
+
+    toDOM(spaces) {
+        spaces = spaces || '';
+        let isOID = (typeof oids === 'object') && (this.tag.isUniversal() && (this.tag.tagNumber == 0x06) || (this.tag.tagNumber == 0x0D));
+        let node = DOM.tag('div', 'node');
+        node.asn1 = this;
+        let head = DOM.tag('div', 'head');
+        head.innerHTML = "<span class='spaces'>" + spaces + '</span>' + this.typeName().replace(/_/g, ' ');
+        let content = this.content(contentLength);
+        let oid;
+        if (content !== null) {
+            let preview = DOM.tag('span', 'preview'),
+                shortContent;
+            if (isOID)
+                content = content.split('\n', 1)[0];
+            shortContent = (content.length > lineLength) ? content.substring(0, lineLength) + DOM.ellipsis : content;
+            preview.appendChild(DOM.space());
+            preview.appendChild(DOM.text(shortContent));
+            if (isOID) {
+                oid = oids[content];
+                if (oid) {
+                    if (oid.d) {
+                        preview.appendChild(DOM.space());
+                        let oidd = DOM.tag('span', 'oid description');
+                        oidd.appendChild(DOM.text(oid.d));
+                        preview.appendChild(oidd);
+                    }
+                    if (oid.c) {
+                        preview.appendChild(DOM.space());
+                        let oidc = DOM.tag('span', 'oid comment');
+                        oidc.appendChild(DOM.text('(' + oid.c + ')'));
+                        preview.appendChild(oidc);
+                    }
                 }
             }
+            head.appendChild(preview);
+            content = DOM.breakLines(content, lineLength);
+            content = content.replace(/</g, '&lt;');
+            content = content.replace(/\n/g, '<br>');
         }
-        head.appendChild(preview);
-        content = DOM.breakLines(content, lineLength);
-        content = content.replace(/</g, '&lt;');
-        content = content.replace(/\n/g, '<br>');
-    }
-    node.appendChild(head);
-    this.node = node;
-    this.head = head;
-    let value = DOM.tag('div', 'value');
-    let s = 'Offset: ' + this.stream.pos + '<br>';
-    s += 'Length: ' + this.header + '+';
-    if (this.length >= 0)
-        s += this.length;
-    else
-        s += (-this.length) + ' (undefined)';
-    if (this.tag.tagConstructed)
-        s += '<br>(constructed)';
-    else if ((this.tag.isUniversal() && ((this.tag.tagNumber == 0x03) || (this.tag.tagNumber == 0x04))) && (this.sub !== null))
-        s += '<br>(encapsulates)';
-    //TODO if (this.tag.isUniversal() && this.tag.tagNumber == 0x03) s += "Unused bits: "
-    if (content !== null) {
-        s += '<br>Value:<br><b>' + content + '</b>';
-        if (isOID && oid) {
-            if (oid.d) s += '<br>' + oid.d;
-            if (oid.c) s += '<br>' + oid.c;
-            if (oid.w) s += '<br>(warning!)';
+        node.appendChild(head);
+        this.node = node;
+        this.head = head;
+        let value = DOM.tag('div', 'value');
+        let s = 'Offset: ' + this.stream.pos + '<br>';
+        s += 'Length: ' + this.header + '+';
+        if (this.length >= 0)
+            s += this.length;
+        else
+            s += (-this.length) + ' (undefined)';
+        if (this.tag.tagConstructed)
+            s += '<br>(constructed)';
+        else if ((this.tag.isUniversal() && ((this.tag.tagNumber == 0x03) || (this.tag.tagNumber == 0x04))) && (this.sub !== null))
+            s += '<br>(encapsulates)';
+        //TODO if (this.tag.isUniversal() && this.tag.tagNumber == 0x03) s += "Unused bits: "
+        if (content !== null) {
+            s += '<br>Value:<br><b>' + content + '</b>';
+            if (isOID && oid) {
+                if (oid.d) s += '<br>' + oid.d;
+                if (oid.c) s += '<br>' + oid.c;
+                if (oid.w) s += '<br>(warning!)';
+            }
         }
-    }
-    value.innerHTML = s;
-    node.appendChild(value);
-    let sub = DOM.tag('div', 'sub');
-    if (this.sub !== null) {
-        spaces += '\xA0 ';
-        for (let i = 0, max = this.sub.length; i < max; ++i)
-            sub.appendChild(this.sub[i].toDOM(spaces));
-    }
-    node.appendChild(sub);
-    head.onclick = function () {
-        node.className = (node.className == 'node collapsed') ? 'node' : 'node collapsed';
-    };
-    return node;
-};
-ASN1.prototype.fakeHover = function (current) {
-    this.node.className += ' hover';
-    if (current)
-        this.head.className += ' hover';
-};
-ASN1.prototype.fakeOut = function (current) {
-    let re = / ?hover/;
-    this.node.className = this.node.className.replace(re, '');
-    if (current)
-        this.head.className = this.head.className.replace(re, '');
-};
-ASN1.prototype.toHexDOM_sub = function (node, className, stream, start, end) {
-    if (start >= end)
-        return;
-    let sub = DOM.tag('span', className);
-    sub.appendChild(DOM.text(
-        stream.hexDump(start, end)));
-    node.appendChild(sub);
-};
-ASN1.prototype.toHexDOM = function (root) {
-    let node = DOM.tag('span', 'hex');
-    if (root === undefined) root = node;
-    this.head.hexNode = node;
-    this.head.onmouseover = function () { this.hexNode.className = 'hexCurrent'; };
-    this.head.onmouseout  = function () { this.hexNode.className = 'hex'; };
-    node.asn1 = this;
-    node.onmouseover = function () {
-        let current = !root.selected;
-        if (current) {
-            root.selected = this.asn1;
-            this.className = 'hexCurrent';
+        value.innerHTML = s;
+        node.appendChild(value);
+        let sub = DOM.tag('div', 'sub');
+        if (this.sub !== null) {
+            spaces += '\xA0 ';
+            for (let i = 0, max = this.sub.length; i < max; ++i)
+                sub.appendChild(this.sub[i].toDOM(spaces));
         }
-        this.asn1.fakeHover(current);
+        node.appendChild(sub);
+        head.onclick = function () {
+            node.className = (node.className == 'node collapsed') ? 'node' : 'node collapsed';
+        };
+        return node;
     };
-    node.onmouseout  = function () {
-        let current = (root.selected == this.asn1);
-        this.asn1.fakeOut(current);
-        if (current) {
-            root.selected = null;
-            this.className = 'hex';
-        }
+    fakeHover(current) {
+        this.node.className += ' hover';
+        if (current)
+            this.head.className += ' hover';
+    };
+    fakeOut(current) {
+        let re = / ?hover/;
+        this.node.className = this.node.className.replace(re, '');
+        if (current)
+            this.head.className = this.head.className.replace(re, '');
     };
-    if (root == node) {
-        let lineStart = this.posStart() & 0xF;
-        if (lineStart != 0) {
-            let skip = DOM.tag('span', 'skip');
-            let skipStr = '';
-            for (let j = lineStart; j > 0; --j)
-                skipStr += '   ';
-            if (lineStart >= 8)
-                skipStr += ' ';
-            skip.innerText = skipStr;
-            node.appendChild(skip);
+    toHexDOM_sub(node, className, stream, start, end) {
+        if (start >= end)
+            return;
+        let sub = DOM.tag('span', className);
+        sub.appendChild(DOM.text(
+            stream.hexDump(start, end)));
+        node.appendChild(sub);
+    };
+    toHexDOM(root) {
+        let node = DOM.tag('span', 'hex');
+        if (root === undefined) root = node;
+        this.head.hexNode = node;
+        this.head.onmouseover = function () { this.hexNode.className = 'hexCurrent'; };
+        this.head.onmouseout  = function () { this.hexNode.className = 'hex'; };
+        node.asn1 = this;
+        node.onmouseover = function () {
+            let current = !root.selected;
+            if (current) {
+                root.selected = this.asn1;
+                this.className = 'hexCurrent';
+            }
+            this.asn1.fakeHover(current);
+        };
+        node.onmouseout  = function () {
+            let current = (root.selected == this.asn1);
+            this.asn1.fakeOut(current);
+            if (current) {
+                root.selected = null;
+                this.className = 'hex';
+            }
+        };
+        if (root == node) {
+            let lineStart = this.posStart() & 0xF;
+            if (lineStart != 0) {
+                let skip = DOM.tag('span', 'skip');
+                let skipStr = '';
+                for (let j = lineStart; j > 0; --j)
+                    skipStr += '   ';
+                if (lineStart >= 8)
+                    skipStr += ' ';
+                skip.innerText = skipStr;
+                node.appendChild(skip);
+            }
         }
+        this.toHexDOM_sub(node, 'tag', this.stream, this.posStart(), this.posLen());
+        this.toHexDOM_sub(node, (this.length >= 0) ? 'dlen' : 'ulen', this.stream, this.posLen(), this.posContent());
+        if (this.sub === null) {
+            let start = this.posContent();
+            let end = this.posEnd();
+            if (end - start < 10 * 16)
+                node.appendChild(DOM.text(
+                    this.stream.hexDump(start, end)));
+            else {
+                let end1 = start + 5 * 16 - (start & 0xF);
+                let start2 = end - 16 - (end & 0xF);
+                node.appendChild(DOM.text(
+                    this.stream.hexDump(start, end1)));
+                let sub = DOM.tag('span', 'skip');
+                sub.appendChild(DOM.text('\u2026 skipping ' + (start2 - end1) + ' bytes \u2026\n'));
+                node.appendChild(sub);
+                node.appendChild(DOM.text(
+                    this.stream.hexDump(start2, end)));
+            }
+        } else if (this.sub.length > 0) {
+            let first = this.sub[0];
+            let last = this.sub[this.sub.length - 1];
+            this.toHexDOM_sub(node, 'intro', this.stream, this.posContent(), first.posStart());
+            for (let i = 0, max = this.sub.length; i < max; ++i)
+                node.appendChild(this.sub[i].toHexDOM(root));
+            this.toHexDOM_sub(node, 'outro', this.stream, last.posEnd(), this.posEnd());
+        } else
+            this.toHexDOM_sub(node, 'outro', this.stream, this.posContent(), this.posEnd());
+        return node;
+    };
+    static decode(stream, offset) {
+        return ASN1.decode(stream, offset, ASN1DOM);
     }
-    this.toHexDOM_sub(node, 'tag', this.stream, this.posStart(), this.posLen());
-    this.toHexDOM_sub(node, (this.length >= 0) ? 'dlen' : 'ulen', this.stream, this.posLen(), this.posContent());
-    if (this.sub === null) {
-        let start = this.posContent();
-        let end = this.posEnd();
-        if (end - start < 10 * 16)
-            node.appendChild(DOM.text(
-                this.stream.hexDump(start, end)));
-        else {
-            let end1 = start + 5 * 16 - (start & 0xF);
-            let start2 = end - 16 - (end & 0xF);
-            node.appendChild(DOM.text(
-                this.stream.hexDump(start, end1)));
-            let sub = DOM.tag('span', 'skip');
-            sub.appendChild(DOM.text('\u2026 skipping ' + (start2 - end1) + ' bytes \u2026\n'));
-            node.appendChild(sub);
-            node.appendChild(DOM.text(
-                this.stream.hexDump(start2, end)));
-        }
-    } else if (this.sub.length > 0) {
-        let first = this.sub[0];
-        let last = this.sub[this.sub.length - 1];
-        this.toHexDOM_sub(node, 'intro', this.stream, this.posContent(), first.posStart());
-        for (let i = 0, max = this.sub.length; i < max; ++i)
-            node.appendChild(this.sub[i].toHexDOM(root));
-        this.toHexDOM_sub(node, 'outro', this.stream, last.posEnd(), this.posEnd());
-    } else
-        this.toHexDOM_sub(node, 'outro', this.stream, this.posContent(), this.posEnd());
-    return node;
-};
+
+}
+
+return ASN1DOM;
 
 });