diff --git a/js.t b/js.t
index e779ccf..9eee9fa 100644
--- a/js.t
+++ b/js.t
@@ -44,6 +44,7 @@
     js_set $test_arg      test_arg;
     js_set $test_iarg     test_iarg;
     js_set $test_var      test_var;
+    js_set $test_type     test_type;
     js_set $test_global   test_global;
     js_set $test_log      test_log;
     js_set $test_except   test_except;
@@ -107,6 +108,10 @@
             js_content request_body;
         }
 
+        location /request_body_cache {
+            js_content request_body_cache;
+        }
+
         location /send {
             js_content send;
         }
@@ -119,6 +124,10 @@
             js_content arg_keys;
         }
 
+        location /type {
+            js_content test_type;
+        }
+
         location /log {
             return 200 $test_log;
         }
@@ -200,6 +209,12 @@
         }
     }
 
+    function request_body_cache(r) {
+        function t(v) {return Buffer.isBuffer(v) ? 'buffer' : (typeof v);}
+        r.return(200,
+                 `requestBody:\${t(r.requestBody)} reqBody:\${t(r.reqBody)}`);
+    }
+
     function send(r) {
         var a, s;
         r.status = 200;
@@ -221,6 +236,13 @@
         r.return(200, Object.keys(r.args).sort());
     }
 
+    function test_type(r) {
+        var p = r.args.path.split('.').reduce((a, v) => a[v], r);
+
+        var type = Buffer.isBuffer(p) ? 'buffer' : (typeof p);
+        r.return(200, `type: \${type}`);
+    }
+
     function test_log(r) {
         r.log('SEE-LOG');
     }
@@ -240,7 +262,7 @@
 
 EOF
 
-$t->try_run('no njs available')->plan(27);
+$t->try_run('no njs available')->plan(32);
 
 ###############################################################################
 
@@ -279,6 +301,24 @@
 
 like(http_get('/arg_keys?b=1&c=2&a=5'), qr/a,b,c/m, 'r.args sorted keys');
 
+TODO: {
+local $TODO = 'not yet'
+	unless http_get('/njs') =~ /^([.0-9]+)$/m && $1 ge '0.5.0';
+
+like(http_get('/type?path=variables.host'), qr/200 OK.*type: string$/s,
+	'variables type');
+like(http_get('/type?path=vars.host'), qr/200 OK.*type: buffer$/s,
+	'vars type');
+
+like(http_post('/type?path=requestBody'), qr/200 OK.*type: string$/s,
+	'requestBody type');
+like(http_post('/type?path=reqBody'), qr/200 OK.*type: buffer$/s,
+	'reqBody type');
+like(http_post('/request_body_cache'), qr/requestBody:string reqBody:buffer$/s,
+	'reqBody type');
+
+}
+
 like(http_get('/var'), qr/variable=127.0.0.1/, 'r.variables');
 like(http_get('/global'), qr/global=njs/, 'global code');
 like(http_get('/log'), qr/200 OK/, 'r.log');
diff --git a/js_buffer.t b/js_buffer.t
new file mode 100644
index 0000000..afc2d1d
--- /dev/null
+++ b/js_buffer.t
@@ -0,0 +1,171 @@
+#!/usr/bin/perl
+
+# (C) Dmitry Volyntsev
+# (C) Nginx, Inc.
+
+# Tests for http njs module, buffer properties.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+use Socket qw/ CRLF /;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+eval { require JSON::PP; };
+plan(skip_all => "JSON::PP not installed") if $@;
+
+my $t = Test::Nginx->new()->has(qw/http rewrite proxy/)
+	->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    js_import test.js;
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location /njs {
+            js_content test.njs;
+        }
+
+        location /return {
+            js_content test.return;
+        }
+
+        location /req_body {
+            js_content test.req_body;
+        }
+
+        location /res_body {
+            js_content test.res_body;
+        }
+
+        location /binary_var {
+            js_content test.binary_var;
+        }
+
+        location /p/ {
+            proxy_pass http://127.0.0.1:8081/;
+        }
+    }
+
+    server {
+        listen       127.0.0.1:8081;
+        server_name  localhost;
+
+        location /sub1 {
+            return 200 '{"a": {"b": 1}}';
+        }
+    }
+}
+
+EOF
+
+$t->write_file('test.js', <<EOF);
+    function test_njs(r) {
+        r.return(200, njs.version);
+    }
+
+    function test_return(r) {
+        var body = Buffer.from("body: ");
+        body = Buffer.concat([body, Buffer.from(r.args.text)]);
+        r.return(200, body);
+    }
+
+    function req_body(r) {
+        var body = r.reqBody;
+        var view = new DataView(body.buffer);
+        view.setInt8(2, 'c'.charCodeAt(0));
+        r.return(200, JSON.parse(body).c.b);
+    }
+
+    function res_body(r) {
+        r.subrequest('/p/sub1')
+        .then(reply => {
+            var body = reply.resBody;
+            var view = new DataView(body.buffer);
+            view.setInt8(2, 'c'.charCodeAt(0));
+            r.return(200, JSON.stringify(JSON.parse(body)));
+        })
+    }
+
+    function binary_var(r) {
+        var test = r.vars.binary_remote_addr.equals(Buffer.from([127,0,0,1]));
+        r.return(200, test);
+    }
+
+    export default {njs: test_njs, return: test_return, req_body, res_body,
+	                binary_var};
+
+EOF
+
+$t->try_run('no njs buffer')->plan(4);
+
+###############################################################################
+
+TODO: {
+local $TODO = 'not yet'
+	unless http_get('/njs') =~ /^([.0-9]+)$/m && $1 ge '0.5.0';
+
+like(http_get('/return?text=FOO'), qr/200 OK.*body: FOO$/s,
+	'return buffer');
+like(http_post('/req_body'), qr/200 OK.*BAR$/s, 'req body');
+is(get_json('/res_body'), '{"c":{"b":1}}', 'res body');
+like(http_get('/binary_var'), qr/200 OK.*true$/s,
+	'binary var');
+
+}
+
+###############################################################################
+
+sub recode {
+	my $json;
+	eval { $json = JSON::PP::decode_json(shift) };
+
+	if ($@) {
+		return "<failed to parse JSON>";
+	}
+
+	JSON::PP->new()->canonical()->encode($json);
+}
+
+sub get_json {
+	http_get(shift) =~ /\x0d\x0a?\x0d\x0a?(.*)/ms;
+	recode($1);
+}
+
+sub http_post {
+	my ($url, %extra) = @_;
+
+	my $p = "POST $url HTTP/1.0" . CRLF .
+		"Host: localhost" . CRLF .
+		"Content-Length: 17" . CRLF .
+		CRLF .
+		"{\"a\":{\"b\":\"BAR\"}}";
+
+	return http($p, %extra);
+}
+
+###############################################################################
diff --git a/stream_js_buffer.t b/stream_js_buffer.t
new file mode 100644
index 0000000..7ade41a
--- /dev/null
+++ b/stream_js_buffer.t
@@ -0,0 +1,179 @@
+#!/usr/bin/perl
+
+# (C) Dmitry Volyntsev
+# (C) Nginx, Inc.
+
+# Tests for stream njs module, buffer properties.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx;
+use Test::Nginx::Stream qw/ stream /;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+my $t = Test::Nginx->new()->has(qw/http proxy rewrite stream stream_return/)
+	->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    js_import test.js;
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location /njs {
+            js_content test.njs;
+        }
+
+        location /p/ {
+            proxy_pass http://127.0.0.1:8085/;
+        }
+
+        location /return {
+            return 200 'RETURN:$http_foo';
+        }
+    }
+}
+
+stream {
+    js_import test.js;
+
+    js_set $type        test.type;
+    js_set $binary_var  test.binary_var;
+
+    server {
+        listen  127.0.0.1:8081;
+        return  $type;
+    }
+
+    server {
+        listen  127.0.0.1:8082;
+        return  $binary_var;
+    }
+
+    server {
+        listen      127.0.0.1:8083;
+        js_preread  test.cb_mismatch;
+        proxy_pass  127.0.0.1:8090;
+    }
+
+    server {
+        listen      127.0.0.1:8084;
+        js_preread  test.cb_mismatch2;
+        proxy_pass  127.0.0.1:8090;
+    }
+
+    server {
+        listen      127.0.0.1:8085;
+        js_filter   test.header_inject;
+        proxy_pass  127.0.0.1:8080;
+    }
+}
+
+EOF
+
+$t->write_file('test.js', <<EOF);
+    function test_njs(r) {
+        r.return(200, njs.version);
+    }
+
+    function type(s) {
+		var v = s.vars.remote_addr;
+		var type = Buffer.isBuffer(v) ? 'buffer' : (typeof v);
+		return type;
+    }
+
+    function binary_var(s) {
+        var test = s.vars.binary_remote_addr.equals(Buffer.from([127,0,0,1]));
+        return test;
+    }
+
+    function cb_mismatch(s) {
+        try {
+            s.on('upload', () => {});
+            s.on('downstream', () => {});
+        } catch (e) {
+            throw new Error(`cb_mismatch:\${e.message}`)
+        }
+    }
+
+    function cb_mismatch2(s) {
+        try {
+            s.on('upstream', () => {});
+            s.on('download', () => {});
+        } catch (e) {
+            throw new Error(`cb_mismatch2:\${e.message}`)
+        }
+    }
+
+    function header_inject(s) {
+        var req = Buffer.from([]);
+
+        s.on('upstream', function(data, flags) {
+            req = Buffer.concat([req, data]);
+
+            var n = req.indexOf('\\n');
+            if (n != -1) {
+                var rest = req.slice(n + 1);
+                req = req.slice(0, n + 1);
+
+                s.send(req, flags);
+                s.send('Foo: foo\\r\\n', flags);
+                s.send(rest, flags);
+
+                s.off('upstream');
+            }
+        });
+    }
+
+    export default {njs: test_njs, type, binary_var, cb_mismatch, cb_mismatch2,
+                    header_inject};
+
+EOF
+
+$t->try_run('no njs ngx')->plan(5);
+
+###############################################################################
+
+TODO: {
+local $TODO = 'not yet'
+	unless http_get('/njs') =~ /^([.0-9]+)$/m && $1 ge '0.5.0';
+
+is(stream('127.0.0.1:' . port(8081))->read(), 'buffer', 'var type');
+is(stream('127.0.0.1:' . port(8082))->read(), 'true', 'binary var');
+
+stream('127.0.0.1:' . port(8083))->io('x');
+stream('127.0.0.1:' . port(8084))->io('x');
+
+like(http_get('/p/return'), qr/RETURN:foo/, 'injected header');
+
+$t->stop();
+
+ok(index($t->read_file('error.log'), 'cb_mismatch:mixing string and buffer')
+   > 0, 'cb mismatch');
+ok(index($t->read_file('error.log'), 'cb_mismatch2:mixing string and buffer')
+   > 0, 'cb mismatch');
+}
+
+###############################################################################