diff --git a/examples/typescript-interop/README.md b/examples/typescript-interop/README.md
index 0697c6a65d..a2c0d8e451 100644
--- a/examples/typescript-interop/README.md
+++ b/examples/typescript-interop/README.md
@@ -1,10 +1,13 @@
-## Running the example
+# TypeScript Interop
+
+This is an example of calling Roc code from [TypeScript](https://www.typescriptlang.org/) on [Node.js](https://nodejs.org/en/).
+
+## Installation
 
 You'll need to have a C compiler installed, but most operating systems will have one already.
 (e.g. macOS has `clang` installed by default, Linux usually has GCC by default, etc.)
 All of these commands should be run from the same directory as this README file.
 
-### Setup before first build
 
 First, run this to install Node dependencies and generate the Makefile that will be
 used by future commands. (You should only need to run this once.)
@@ -14,7 +17,15 @@ npm install
 npx node-gyp configure
 ```
 
-### Build
+## Building the Roc library
+
+First, `cd` into this directory and run this in your terminal:
+
+```
+roc build --lib
+```
+
+This compiles your Roc code into a binary library in the current directory. The library's filename will be libhello plus an OS-specific extension (e.g. libhello.dylib on macOS).
 
 Next, run this to rebuild the C sources.
 
@@ -34,10 +45,20 @@ You can verify that TypeScript sees the correct types with:
 npx tsc hello.ts
 ```
 
-### Run
+### Try it out!
 
-Now you should be able to run the example with:
+Now that everything is built, you should be able to run the example with:
 
 ```
 npx ts-node hello.ts
-```
\ No newline at end of file
+```
+
+To rebuild after changing either the `demo.`c file or any `.roc` files, run:
+
+```
+roc build --lib && npx node-gyp build
+```
+
+## About this example
+
+This was created by following the [NodeJS addons](https://nodejs.org/dist/latest/docs/api/addons.html) tutorial and switching from C++ to C, then creating the `addon.d.ts` file to add types to the generated native Node module.
\ No newline at end of file
diff --git a/examples/typescript-interop/demo.c b/examples/typescript-interop/demo.c
new file mode 100644
index 0000000000..d305a1e826
--- /dev/null
+++ b/examples/typescript-interop/demo.c
@@ -0,0 +1,252 @@
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <unistd.h>
+#include <node_api.h>
+
+void *roc_alloc(size_t size, unsigned int alignment) { return malloc(size); }
+
+void *roc_realloc(void *ptr, size_t new_size, size_t old_size,
+                  unsigned int alignment)
+{
+    return realloc(ptr, new_size);
+}
+
+void roc_dealloc(void *ptr, unsigned int alignment) { free(ptr); }
+
+__attribute__((noreturn)) void roc_panic(void *ptr, unsigned int alignment)
+{
+    rb_raise(rb_eException, "%s", (char *)ptr);
+}
+
+void *roc_memcpy(void *dest, const void *src, size_t n)
+{
+    return memcpy(dest, src, n);
+}
+
+void *roc_memset(void *str, int c, size_t n) { return memset(str, c, n); }
+
+// Reference counting
+
+// If the refcount is set to this, that means the allocation is
+// stored in readonly memory in the binary, and we must not
+// attempt to increment or decrement it; if we do, we'll segfault!
+const ssize_t REFCOUNT_READONLY = 0;
+const ssize_t REFCOUNT_ONE = (ssize_t)PTRDIFF_MIN;
+const size_t MASK = (size_t)PTRDIFF_MIN;
+
+// Increment reference count, given a pointer to the first element in a collection.
+// We don't need to check for overflow because in order to overflow a usize worth of refcounts,
+// you'd need to somehow have more pointers in memory than the OS's virtual address space can hold.
+void incref(uint8_t* bytes, uint32_t alignment)
+{
+    ssize_t *refcount_ptr = ((ssize_t *)bytes) - 1;
+    ssize_t refcount = *refcount_ptr;
+
+    if (refcount != REFCOUNT_READONLY) {
+        *refcount_ptr = refcount + 1;
+    }
+}
+
+// Decrement reference count, given a pointer to the first element in a collection.
+// Then call roc_dealloc if nothing is referencing this collection anymore.
+void decref(uint8_t* bytes, uint32_t alignment)
+{
+    if (bytes == NULL) {
+        return;
+    }
+
+    size_t extra_bytes = (sizeof(size_t) >= (size_t)alignment) ? sizeof(size_t) : (size_t)alignment;
+    ssize_t *refcount_ptr = ((ssize_t *)bytes) - 1;
+    ssize_t refcount = *refcount_ptr;
+
+    if (refcount != REFCOUNT_READONLY) {
+        *refcount_ptr = refcount - 1;
+
+        if (refcount == REFCOUNT_ONE) {
+            void *original_allocation = (void *)(refcount_ptr - (extra_bytes - sizeof(size_t)));
+
+            roc_dealloc(original_allocation, alignment);
+        }
+    }
+}
+
+// RocBytes (List U8)
+
+struct RocBytes
+{
+    uint8_t *bytes;
+    size_t len;
+    size_t capacity;
+};
+
+struct RocBytes init_rocbytes(uint8_t *bytes, size_t len)
+{
+    if (len == 0)
+    {
+        struct RocBytes ret = {
+            .len = 0,
+            .bytes = NULL,
+            .capacity = MASK,
+        };
+
+        return ret;
+    }
+    else
+    {
+        struct RocBytes ret;
+        size_t refcount_size = sizeof(size_t);
+        uint8_t *new_content = (uint8_t *)roc_alloc(len + refcount_size, alignof(size_t)) + refcount_size;
+
+        memcpy(new_content, bytes, len);
+
+        ret.bytes = new_content;
+        ret.len = len;
+        ret.capacity = len;
+
+        return ret;
+    }
+}
+
+// RocStr
+
+struct RocStr
+{
+    uint8_t *bytes;
+    size_t len;
+    size_t capacity;
+};
+
+struct RocStr init_rocstr(uint8_t *bytes, size_t len)
+{
+    if (len == 0)
+    {
+        struct RocStr ret = {
+            .len = 0,
+            .bytes = NULL,
+            .capacity = MASK,
+        };
+
+        return ret;
+    }
+    else if (len < sizeof(struct RocStr))
+    {
+        // Start out with zeroed memory, so that
+        // if we end up comparing two small RocStr values
+        // for equality, we won't risk memory garbage resulting
+        // in two equal strings appearing unequal.
+        struct RocStr ret = {
+            .len = 0,
+            .bytes = NULL,
+            .capacity = MASK,
+        };
+
+        // Copy the bytes into the stack allocation
+        memcpy(&ret, bytes, len);
+
+        // Record the string's length in the last byte of the stack allocation
+        ((uint8_t *)&ret)[sizeof(struct RocStr) - 1] = (uint8_t)len | 0b10000000;
+
+        return ret;
+    }
+    else
+    {
+        // A large RocStr is the same as a List U8 (aka RocBytes) in memory.
+        struct RocBytes roc_bytes = init_rocbytes(bytes, len);
+
+        struct RocStr ret = {
+            .len = roc_bytes.len,
+            .bytes = roc_bytes.bytes,
+            .capacity = roc_bytes.capacity,
+        };
+
+        return ret;
+    }
+}
+
+bool is_small_str(struct RocStr str) { return ((ssize_t)str.capacity) < 0; }
+
+// Determine the length of the string, taking into
+// account the small string optimization
+size_t roc_str_len(struct RocStr str)
+{
+    uint8_t *bytes = (uint8_t *)&str;
+    uint8_t last_byte = bytes[sizeof(str) - 1];
+    uint8_t last_byte_xored = last_byte ^ 0b10000000;
+    size_t small_len = (size_t)(last_byte_xored);
+    size_t big_len = str.len;
+
+    // Avoid branch misprediction costs by always
+    // determining both small_len and big_len,
+    // so this compiles to a cmov instruction.
+    if (is_small_str(str))
+    {
+        return small_len;
+    }
+    else
+    {
+        return big_len;
+    }
+}
+
+extern void roc__mainForHost_1_exposed_generic(struct RocBytes *ret, struct RocBytes *arg);
+
+// Receive a value from Ruby, JSON serialized it and pass it to Roc as a List U8
+// (at which point the Roc platform will decode it and crash if it's invalid,
+// which roc_panic will translate into a Ruby exception), then get some JSON back from Roc
+// - also as a List U8 - and have Ruby JSON.parse it into a plain Ruby value to return.
+VALUE call_roc(VALUE self, VALUE rb_arg)
+{
+    // This must be required before the to_json method will exist on String.
+    rb_require("json");
+
+    // Turn the given Ruby value into a JSON string.
+    // TODO should we defensively encode it as UTF-8 first?
+    VALUE json_arg = rb_funcall(rb_arg, rb_intern("to_json"), 0);
+
+    struct RocBytes arg = init_rocbytes((uint8_t *)RSTRING_PTR(json_arg), RSTRING_LEN(json_arg));
+    struct RocBytes ret;
+
+    // Call the Roc function to populate `ret`'s bytes.
+    roc__mainForHost_1_exposed_generic(&ret, &arg);
+
+    // Create a rb_utf8_str from the heap-allocated JSON bytes the Roc function returned.
+    VALUE returned_json = rb_utf8_str_new((char *)ret.bytes, ret.len);
+
+    // Now that we've created our Ruby JSON string, we're no longer referencing the RocBytes.
+    decref((void *)&ret, alignof(uint8_t *));
+
+    return rb_funcall(rb_define_module("JSON"), rb_intern("parse"), 1, returned_json);
+}
+
+void Init_demo()
+{
+    VALUE roc_app = rb_define_module("RocApp");
+    rb_define_module_function(roc_app, "call_roc", &call_roc, 1);
+}
+
+napi_value Method(napi_env env, napi_callback_info args) {
+  napi_value greeting;
+  napi_status status;
+
+  status = napi_create_string_utf8(env, "World!", NAPI_AUTO_LENGTH, &greeting);
+  if (status != napi_ok) return NULL;
+  return greeting;
+}
+
+napi_value init(napi_env env, napi_value exports) {
+  napi_status status;
+  napi_value fn;
+
+  status = napi_create_function(env, NULL, 0, Method, NULL, &fn);
+  if (status != napi_ok) return NULL;
+
+  status = napi_set_named_property(env, exports, "hello", fn);
+  if (status != napi_ok) return NULL;
+  return exports;
+}
+
+NAPI_MODULE(NODE_GYP_MODULE_NAME, init)
\ No newline at end of file
diff --git a/examples/typescript-interop/main.roc b/examples/typescript-interop/main.roc
new file mode 100644
index 0000000000..311d89a74c
--- /dev/null
+++ b/examples/typescript-interop/main.roc
@@ -0,0 +1,13 @@
+app "libhello"
+    packages { pf: "platform/main.roc" }
+    imports []
+    provides [main] to pf
+
+main : U64 -> Str
+main = \num ->
+    if num == 0 then
+        "I need a positive number here!"
+    else
+        str = Num.toStr num
+
+        "The number was \(str), OH YEAH!!! 🤘🤘"
\ No newline at end of file