Node util/types.isExternal function | API Reference | Bun

Returns true if the value is a native External value.

A native External value is a special type of object that contains a raw C++ pointer (void*) for access from native code, and has no other properties. Such objects are created either by Node.js internals or native addons. In JavaScript, they are frozen objects with a null prototype.

#include js_native_api.h>
#include stdlib.h>
napi_value result;
static napi_value MyNapi(napi_env env, napi_callback_info info) {
int* raw = (int*) malloc(1024);
napi_status status = napi_create_external(env, (void*) raw, NULL, NULL, &result);
if (status != napi_ok) {
napi_throw_error(env, NULL, "napi_create_external failed");
return NULL;
}
return result;
}
...
DECLARE_NAPI_PROPERTY("myNapi", MyNapi)
...

import native from 'napi_addon.node';
import { types } from 'node:util';

const data = native.myNapi();
types.isExternal(data); // returns true
types.isExternal(0); // returns false
types.isExternal(new String('foo')); // returns false

For further information on napi_create_external, refer to napi_create_external().