Add JavaScript linting and tests

* Add sample malformed JavaScript files to lint on
* In our tests, copy the `node_modules` directory to make `jshint`
  available, then validate that we're correctly linting the staged JS
  file
* In our pre-commit hook, lint the staged JavaScript files. If either of
  our linting commands fail then exit 1 to abort the commit.

1 files changed, 37 insertions, 0 deletions

diff --git a/t/150-javascript.t b/t/150-javascript.t
new file mode 100644
index 0000000..208b497
--- /dev/null
+++ b/t/150-javascript.t
@@ -0,0 +1,37 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+use Test::More;
+
+chdir 't/git-repo/' or die $!;
+
+system('cp -R ../../node_modules .');
+ok !$?;
+
+system('cp ../*.js .');
+ok !$?;
+
+my $output = `ls -1 | grep .*\.js`;
+
+ok $output eq 'test.js
+uncommitted.js
+', 'Both test JavaScript files are present';
+
+system('git add test.js');
+ok !$?;
+
+$output = `git commit 2>&1`;
+
+ok $output eq "test.js: line 1, col 21, Missing semicolon.
+test.js: line 3, col 1, Bad line breaking before '&&'.
+test.js: line 3, col 9, Expected an assignment or function call and instead saw an expression.
+
+3 errors
+", 'jshint ran on committed JavaScript file';
+
+$output = `git reset`;
+ok !$?;
+
+done_testing;