From 1afefdbdfa62de83bfa7334bc78d30c273cd5a93 Mon Sep 17 00:00:00 2001
From: Louis Pilfold <louis@lpil.uk>
Date: Sun, 29 Aug 2021 17:24:59 +0100
Subject: Promise tap

---
 src/gleam/javascript/promise.gleam | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'src')

diff --git a/src/gleam/javascript/promise.gleam b/src/gleam/javascript/promise.gleam
index 4f8d54c..2437dc0 100644
--- a/src/gleam/javascript/promise.gleam
+++ b/src/gleam/javascript/promise.gleam
@@ -1,4 +1,5 @@
 // TODO: docs
+// TODO: labels
 pub external type Promise(value)
 
 pub external fn resolve(value) -> Promise(value) =
@@ -9,3 +10,11 @@ pub external fn then(Promise(a), fn(a) -> Promise(b)) -> Promise(b) =
 
 pub external fn map(Promise(a), fn(a) -> b) -> Promise(b) =
   "../../ffi.js" "map_promise"
+
+pub fn tap(promise: Promise(a), callback: fn(a) -> b) -> Promise(a) {
+  promise
+  |> map(fn(a) {
+    callback(a)
+    a
+  })
+}
-- 
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