WIP

Author: CMCDragonkai

src/native/index.cpp

@@ -1,5 +1,6 @@
 #define NAPI_VERSION 3
 
+#include <string.h>
 #include <node_api.h>
 #include <napi-macros.h>
 
@@ -58,7 +59,6 @@ napi_value addOne (napi_env env, napi_callback_info info) {
   return return_int32;
 }
 
-
 /**
  * Using n-api macros instead removes alot of boilerplate
  * This function is basically the same as `addOne`
@@ -90,7 +90,7 @@ NAPI_METHOD(createArr) {
 NAPI_METHOD(createObj) {
   napi_value obj;
   NAPI_STATUS_THROWS(napi_create_object(env, &obj))
-  // we need to set a string
+  // Set a value on the obj
   napi_value value;
   NAPI_STATUS_THROWS(napi_create_string_utf8(
     env,
@@ -104,9 +104,44 @@ NAPI_METHOD(createObj) {
 
 /**
  * Takes an object and sets a property on it
+ * Object must be { key1: "some string" }
+ * Will return object new property key2
  */
-// NAPI_METHOD(setProperty) {
-// }
+NAPI_METHOD(setProperty) {
+  NAPI_ARGV(1)
+  // Expect an object argument
+  napi_value obj = argv[0];
+  // Extract property key1, and expect it to be a string
+  napi_value keyValue;
+  NAPI_STATUS_THROWS(napi_get_named_property(env, obj, "key1", &keyValue))
+  // Find the JS length of the string
+  size_t keyValueLength;
+  NAPI_STATUS_THROWS(napi_get_value_string_utf8(
+    env,
+    keyValue,
+    NULL,
+    0,
+    &keyValueLength
+  ))
+  // Convert the value to a C string
+  NAPI_UTF8(keyValueString, keyValueLength + 1, keyValue)
+  keyValueString[keyValueLength + 1] = '\0';
+  // Concatenate the string
+  char fullString[8 + keyValueLength + 1] = {0};
+  strcat(fullString, "initial ");
+  strcat(fullString, keyValueString);
+  // Convert the C string back to JS string
+  napi_value fullStringJS;
+  NAPI_STATUS_THROWS(napi_create_string_utf8(
+    env,
+    fullString,
+    NAPI_AUTO_LENGTH,
+    &fullStringJS
+  ))
+  // Set the the new string as new of property key2
+  NAPI_STATUS_THROWS(napi_set_named_property(env, obj, "key2", fullStringJS));
+  return obj;
+}
 
 /**
  * All exported functions
@@ -138,4 +173,5 @@ NAPI_INIT() {
   NAPI_EXPORT_FUNCTION(timesTwo)
   NAPI_EXPORT_FUNCTION(createArr)
   NAPI_EXPORT_FUNCTION(createObj)
+  NAPI_EXPORT_FUNCTION(setProperty)
 }

tests/lib/native.test.ts

@@ -23,4 +23,9 @@ describe('native bindings', () => {
     // https://github.com/facebook/jest/issues/12814
     // expect(native.createObj()).toStrictEqual({ key: 'hello world' });
   });
+  test('set property', () => {
+    expect(
+      native.setProperty({ key1: 'value1' })
+    ).toStrictEqual({ key1: 'value1', key2: 'initial value1'});
+  });
 });