From 39a8ab469a8596a413d75d85e3ed7587783b353d Mon Sep 17 00:00:00 2001
From: Yuriy Glukhov <yglukhov@users.noreply.github.com>
Date: Fri, 21 Dec 2018 23:45:20 +0200
Subject: [PATCH] Fixed insert for nil seq in js (#10068)

---
 lib/system.nim     |  2 +-
 tests/js/test1.nim | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/lib/system.nim b/lib/system.nim
index e998ffee0a..06aa253115 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -1692,7 +1692,7 @@ proc insert*[T](x: var seq[T], item: T, i = 0.Natural) {.noSideEffect.} =
   else:
     when defined(js):
       var it : T
-      {.emit: "`x`.splice(`i`, 0, `it`);".}
+      {.emit: "`x` = `x` || []; `x`.splice(`i`, 0, `it`);".}
     else:
       defaultImpl()
   x[i] = item
diff --git a/tests/js/test1.nim b/tests/js/test1.nim
index 7f1d346f08..73e7a37ed2 100644
--- a/tests/js/test1.nim
+++ b/tests/js/test1.nim
@@ -20,3 +20,35 @@ proc onButtonClick(inputElement: string) {.exportc.} =
 
 onButtonClick(inputElement)
 
+block:
+  var s: string
+  s.add("hi")
+  doAssert(s == "hi")
+
+block:
+  var s: string
+  s.insert("hi", 0)
+  doAssert(s == "hi")
+
+block:
+  var s: string
+  s.setLen(2)
+  s[0] = 'h'
+  s[1] = 'i'
+  doAssert(s == "hi")
+
+block:
+  var s: seq[int]
+  s.setLen(2)
+  doAssert(s == @[0, 0])
+
+block:
+  var s: seq[int]
+  s.insert(2, 0)
+  doAssert(s == @[2])
+
+block:
+  var s: seq[int]
+  s.add(2)
+  doAssert(s == @[2])
+