add reference_equal function

Author: CrowdHailer

src/ffi.mjs

@@ -127,6 +127,10 @@ export function set_reference(ref, value) {
   return previous;
 }
 
+export function reference_equal(a,b) {
+  return a === b
+}
+
 export function all_promises(...promises) {
   if (promises.length === 1) {
     return Promise.all(promises[0]);

src/gleam/javascript.gleam

@@ -35,3 +35,6 @@ pub fn update_reference(ref: Reference(a), f: fn(a) -> a) -> a {
   set_reference(ref, f(value))
   value
 }
+
+@external(javascript, "../ffi.mjs", "reference_equal")
+pub fn reference_equal(a: Reference(a), b: Reference(a)) -> Bool

test/gleam/javascript_test.gleam

@@ -2,6 +2,7 @@ import gleam/javascript.{
   BooleanType, FunctionType, NumberType, ObjectType, StringType, SymbolType,
   UndefinedType,
 }
+import gleeunit/should
 
 pub fn type_of_test() {
   let assert UndefinedType = javascript.type_of(Nil)
@@ -34,3 +35,13 @@ pub fn reference_test() {
   let assert 2 = javascript.set_reference(ref, 3)
   let assert 3 = javascript.dereference(ref)
 }
+
+pub fn reference_equality_test() {
+  javascript.make_reference(0)
+  |> javascript.reference_equal(javascript.make_reference(0))
+  |> should.equal(False)
+
+  let ref = javascript.make_reference(0)
+  javascript.reference_equal(ref, ref)
+  |> should.equal(True)
+}