diff --git a/misc/pbsim-eval.js b/misc/pbsim-eval.js
new file mode 100644
index 0000000..afadc40
--- /dev/null
+++ b/misc/pbsim-eval.js
@@ -0,0 +1,124 @@
+var getopt = function(args, ostr) {
+	var oli; // option letter list index
+	if (typeof(getopt.place) == 'undefined')
+		getopt.ind = 0, getopt.arg = null, getopt.place = -1;
+	if (getopt.place == -1) { // update scanning pointer
+		if (getopt.ind >= args.length || args[getopt.ind].charAt(getopt.place = 0) != '-') {
+			getopt.place = -1;
+			return null;
+		}
+		if (getopt.place + 1 < args[getopt.ind].length && args[getopt.ind].charAt(++getopt.place) == '-') { // found "--"
+			++getopt.ind;
+			getopt.place = -1;
+			return null;
+		}
+	}
+	var optopt = args[getopt.ind].charAt(getopt.place++); // character checked for validity
+	if (optopt == ':' || (oli = ostr.indexOf(optopt)) < 0) {
+		if (optopt == '-') return null; //  if the user didn't specify '-' as an option, assume it means null.
+		if (getopt.place < 0) ++getopt.ind;
+		return '?';
+	}
+	if (oli+1 >= ostr.length || ostr.charAt(++oli) != ':') { // don't need argument
+		getopt.arg = null;
+		if (getopt.place < 0 || getopt.place >= args[getopt.ind].length) ++getopt.ind, getopt.place = -1;
+	} else { // need an argument
+		if (getopt.place >= 0 && getopt.place < args[getopt.ind].length)
+			getopt.arg = args[getopt.ind].substr(getopt.place);
+		else if (args.length <= ++getopt.ind) { // no arg
+			getopt.place = -1;
+			if (ostr.length > 0 && ostr.charAt(0) == ':') return ':';
+			return '?';
+		} else getopt.arg = args[getopt.ind]; // white space
+		getopt.place = -1;
+		++getopt.ind;
+	}
+	return optopt;
+}
+
+var c, max_mapq = 60, mode = 0, err_out_q = 256, print_err = false;
+while ((c = getopt(arguments, "Q:")) != null) {
+	if (c == 'Q') err_out_q = parseInt(getopt.arg), print_err = true;
+}
+
+var file = arguments.length == getopt.ind? new File() : new File(arguments[getopt.ind]);
+var buf = new Bytes();
+
+var tot = [], err = [];
+for (var q = 0; q <= max_mapq; ++q)
+	tot[q] = err[q] = 0;
+
+function is_correct(s, b)
+{
+	if (s[0] != b[0] || s[3] != b[3]) return false;
+	var o, l;
+	if (s[1] < b[1]) {
+		if (s[2] <= b[1]) return false;
+		o = (s[2] < b[2]? s[2] : b[2]) - b[1];
+		l = (s[2] > b[2]? s[2] : b[2]) - s[1];
+	} else {
+		if (b[2] <= s[1]) return false;
+		o = (s[2] < b[2]? s[2] : b[2]) - s[1];
+		l = (s[2] > b[2]? s[2] : b[2]) - b[1];
+	}
+	return o/l > .333? true : false;
+}
+
+function count_err(qname, a, tot, err, mode)
+{
+	var s = qname.split("!");
+	if (s.length < 5 || (s[4] != '+' && s[4] != '-'))
+		throw Error("Failed to parse pbsim2fa read names '" + qname + "'");
+	s[2] = parseInt(s[2]);
+	s[3] = parseInt(s[3]);
+	s.shift(); // skip pbsim orginal read name
+	var max_mapq = 0;
+	for (var i = 0; i < a.length; ++i)
+		if (a[i][4] > max_mapq)
+			max_mapq = a[i][4];
+	++tot[max_mapq];
+	if (mode == 0) { // longest only
+		var max = 0, max_i = -1;
+		for (var i = 0; i < a.length; ++i)
+			if (a[i][2] - a[i][1] > max)
+				max = a[i][2] - a[i][1], max_i = i;
+		if (!is_correct(s, a[max_i])) {
+			if (max_mapq >= err_out_q)
+				print(qname, a[max_i].join("\t"));
+			++err[max_mapq];
+		}
+	}
+}
+
+var lineno = 0, last = null, a = [];
+while (file.readline(buf) >= 0) {
+	var line = buf.toString();
+	++lineno;
+	if (line[0] != '@') {
+		var t = line.split("\t");
+		if (last != t[0]) {
+			if (last != null) count_err(last, a, tot, err, mode);
+			a = [], last = t[0];
+		}
+		if (t[4] == '+' || t[4] == '-') { // PAF
+			if (/\ts1:i:\d+/.test(line) && !/\ts2:i:\d+/.test(line)) // secondary alignment in minimap2 PAF
+				continue;
+			var mapq = parseInt(t[11]);
+			if (mapq > max_mapq) mapq = max_mapq;
+			a.push([t[5], parseInt(t[7]), parseInt(t[8]), t[4], mapq]);
+		}
+	}
+}
+if (last != null) count_err(last, a, tot, err, mode);
+
+buf.destroy();
+file.close();
+
+if (!print_err) {
+	var sum_tot = 0, sum_err = 0;
+	for (var q = max_mapq; q >= 0; --q) {
+		if (tot[q] == 0) continue;
+		sum_tot += tot[q], sum_err += err[q];
+		print(q, tot[q], err[q], sum_tot, sum_err, sum_err/sum_tot);
+	}
+}