2 files changed, 47 insertions, 13 deletions
diff --git a/std/bytes/mod.ts b/std/bytes/mod.ts
index 0157b39a5..88eb97710 100644
--- a/std/bytes/mod.ts
+++ b/std/bytes/mod.ts
@@ -7,8 +7,8 @@ export function findIndex(a: Uint8Array, pat: Uint8Array): number {
   for (let i = 0; i < a.length; i++) {
     if (a[i] !== s) continue;
     const pin = i;
-    let matched = 1,
-      j = i;
+    let matched = 1;
+    let j = i;
     while (matched < pat.length) {
       j++;
       if (a[j] !== pat[j - pin]) {
@@ -29,8 +29,8 @@ export function findLastIndex(a: Uint8Array, pat: Uint8Array): number {
   for (let i = a.length - 1; i >= 0; i--) {
     if (a[i] !== e) continue;
     const pin = i;
-    let matched = 1,
-      j = i;
+    let matched = 1;
+    let j = i;
     while (matched < pat.length) {
       j--;
       if (a[j] !== pat[pat.length - 1 - (pin - j)]) {
@@ -94,3 +94,11 @@ export function repeat(b: Uint8Array, count: number): Uint8Array {
 
   return nb;
 }
+
+/** Concatenate two binary arrays and return new one  */
+export function concat(a: Uint8Array, b: Uint8Array): Uint8Array {
+  const output = new Uint8Array(a.length + b.length);
+  output.set(a, 0);
+  output.set(b, a.length);
+  return output;
+}
diff --git a/std/bytes/test.ts b/std/bytes/test.ts
index c1609ebdc..3ded0cd85 100644
--- a/std/bytes/test.ts
+++ b/std/bytes/test.ts
@@ -1,9 +1,17 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { findIndex, findLastIndex, equal, hasPrefix, repeat } from "./mod.ts";
-import { assertEquals, assertThrows } from "../testing/asserts.ts";
+import {
+  findIndex,
+  findLastIndex,
+  equal,
+  hasPrefix,
+  repeat,
+  concat
+} from "./mod.ts";
+import { assertEquals, assertThrows, assert } from "../testing/asserts.ts";
+import { encode, decode } from "../strings/mod.ts";
 
-Deno.test(function bytesfindIndex1(): void {
+Deno.test("[bytes] findIndex1", () => {
   const i = findIndex(
     new Uint8Array([1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 3]),
     new Uint8Array([0, 1, 2])
@@ -11,12 +19,12 @@ Deno.test(function bytesfindIndex1(): void {
   assertEquals(i, 2);
 });
 
-Deno.test(function bytesfindIndex2(): void {
+Deno.test("[bytes] findIndex2", () => {
   const i = findIndex(new Uint8Array([0, 0, 1]), new Uint8Array([0, 1]));
   assertEquals(i, 1);
 });
 
-Deno.test(function bytesfindLastIndex1(): void {
+Deno.test("[bytes] findLastIndex1", () => {
   const i = findLastIndex(
     new Uint8Array([0, 1, 2, 0, 1, 2, 0, 1, 3]),
     new Uint8Array([0, 1, 2])
@@ -24,22 +32,22 @@ Deno.test(function bytesfindLastIndex1(): void {
   assertEquals(i, 3);
 });
 
-Deno.test(function bytesfindLastIndex2(): void {
+Deno.test("[bytes] findLastIndex2", () => {
   const i = findLastIndex(new Uint8Array([0, 1, 1]), new Uint8Array([0, 1]));
   assertEquals(i, 0);
 });
 
-Deno.test(function bytesBytesequal(): void {
+Deno.test("[bytes] equal", () => {
   const v = equal(new Uint8Array([0, 1, 2, 3]), new Uint8Array([0, 1, 2, 3]));
   assertEquals(v, true);
 });
 
-Deno.test(function byteshasPrefix(): void {
+Deno.test("[bytes] hasPrefix", () => {
   const v = hasPrefix(new Uint8Array([0, 1, 2]), new Uint8Array([0, 1]));
   assertEquals(v, true);
 });
 
-Deno.test(function bytesrepeat(): void {
+Deno.test("[bytes] repeat", () => {
   // input / output / count / error message
   const repeatTestCase = [
     ["", "", 0],
@@ -71,3 +79,21 @@ Deno.test(function bytesrepeat(): void {
     }
   }
 });
+
+Deno.test("[bytes] concat", () => {
+  const u1 = encode("Hello ");
+  const u2 = encode("World");
+  const joined = concat(u1, u2);
+  assertEquals(decode(joined), "Hello World");
+  assert(u1 !== joined);
+  assert(u2 !== joined);
+});
+
+Deno.test("[bytes] concat empty arrays", () => {
+  const u1 = new Uint8Array();
+  const u2 = new Uint8Array();
+  const joined = concat(u1, u2);
+  assertEquals(joined.byteLength, 0);
+  assert(u1 !== joined);
+  assert(u2 !== joined);
+});