From 9f7a6e116ac40e725644b78bb265fc041cc1ef16 Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Fri, 22 May 2020 14:01:35 +0100
Subject: [PATCH] LibJS: Let Array.prototype.join() ignore additional arguments

I.e.

array.join("x", "y", "z") === array.join("x")

rather than

array.join("x", "y", "z") === array.join()
---
 Libraries/LibJS/Runtime/ArrayPrototype.cpp    | 2 +-
 Libraries/LibJS/Tests/Array.prototype.join.js | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/Libraries/LibJS/Runtime/ArrayPrototype.cpp b/Libraries/LibJS/Runtime/ArrayPrototype.cpp
index 4be61e58ab..b9ff84a0ab 100644
--- a/Libraries/LibJS/Runtime/ArrayPrototype.cpp
+++ b/Libraries/LibJS/Runtime/ArrayPrototype.cpp
@@ -239,7 +239,7 @@ Value ArrayPrototype::join(Interpreter& interpreter)
         return {};
 
     String separator = ",";
-    if (interpreter.argument_count() == 1) {
+    if (interpreter.argument_count()) {
         separator = interpreter.argument(0).to_string(interpreter);
         if (interpreter.exception())
             return {};
diff --git a/Libraries/LibJS/Tests/Array.prototype.join.js b/Libraries/LibJS/Tests/Array.prototype.join.js
index 0221aacfd3..fc82deb20c 100644
--- a/Libraries/LibJS/Tests/Array.prototype.join.js
+++ b/Libraries/LibJS/Tests/Array.prototype.join.js
@@ -5,6 +5,7 @@ try {
 
     assert(["hello", "friends"].join() === "hello,friends");
     assert(["hello", "friends"].join(" ") === "hello friends");
+    assert(["hello", "friends", "foo"].join("~", "#") === "hello~friends~foo");
     assert([].join() === "");
     assert([null].join() === "");
     assert([undefined].join() === "");