diff --git a/README.md b/README.md
index 7a6a03b7..10ff4627 100644
--- a/README.md
+++ b/README.md
@@ -31,9 +31,11 @@ wp i18n
 Create a POT file for a WordPress plugin or theme.
 
 ~~~
-wp i18n make-pot <source> [<destination>] [--slug=<slug>] [--domain=<domain>] [--merge[=<file>]] [--exclude=<paths>]
+wp i18n make-pot <source> [<destination>] [--slug=<slug>] [--domain=<domain>] [--merge[=<file>]] [--exclude=<paths>] [--skip-js]
 ~~~
 
+Scans PHP and JavaScript files, as well as theme stylesheets for translatable strings.
+
 **OPTIONS**
 
 	<source>
@@ -57,6 +59,9 @@ wp i18n make-pot <source> [<destination>] [--slug=<slug>] [--domain=<domain>] [-
 		By default, the following files and folders are ignored: node_modules, .git, .svn, .CVS, .hg, vendor.
 		Leading and trailing slashes are ignored, i.e. `/my/directory/` is the same as `my/directory`.
 
+	[--skip-js]
+		Skips JavaScript string extraction. Useful when this is done in another build step, e.g. through Babel.
+
 **EXAMPLES**
 
     # Create a POT file for the WordPress plugin/theme in the current directory
diff --git a/composer.json b/composer.json
index c5e0fa46..aeb0d2e7 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,8 @@
         ]
     },
     "require": {
-        "gettext/gettext": "dev-master#37882dc3b58c2357fc6ddc204c1f22f7bb2b6601"
+        "gettext/gettext": "dev-master#37882dc3b58c2357fc6ddc204c1f22f7bb2b6601",
+        "mck89/peast": "^1.8"
     },
     "require-dev": {
         "wp-cli/wp-cli": "^1.1.0",
diff --git a/features/makepot.feature b/features/makepot.feature
index ef93cc51..097ce661 100644
--- a/features/makepot.feature
+++ b/features/makepot.feature
@@ -66,6 +66,7 @@ Feature: Generate a POT file of a WordPress plugin
       """
       Description of the plugin
       """
+
   Scenario: Adds copyright comments
     When I run `wp scaffold plugin hello-world`
 
@@ -188,12 +189,20 @@ Feature: Generate a POT file of a WordPress plugin
 
        __( 'Hello World', 'foo-plugin' );
       """
+    And a foo-plugin/foo-plugin.js file:
+      """
+      __( 'Hello World', 'foo-plugin' );
+      """
 
     When I run `wp i18n make-pot foo-plugin foo-plugin.pot`
     And the foo-plugin.pot file should contain:
       """
       #: foo-plugin.php:15
       """
+    And the foo-plugin.pot file should contain:
+      """
+      #: foo-plugin.js:1
+      """
 
   Scenario: Uses the current folder as destination path when none is set.
     When I run `wp scaffold plugin hello-world`
@@ -401,14 +410,6 @@ Feature: Generate a POT file of a WordPress plugin
       """
       msgid_plural "__ngettext_noop_plural"
       """
-    And the foo-plugin/foo-plugin.pot file should contain:
-      """
-      msgid "__"
-      """
-    And the foo-plugin/foo-plugin.pot file should contain:
-      """
-      msgid "__"
-      """
     And the foo-plugin/foo-plugin.pot file should not contain:
       """
       msgid "__unsupported_func"
@@ -447,7 +448,7 @@ Feature: Generate a POT file of a WordPress plugin
 
        /* translators: this should get extracted. */ $foo = __( 'baba', 'foo-plugin' );
 
-       /* translators: boo */ /* translators: this should get extracted too. */ /* some other comment */ $bar = g ( __( 'baba', 'foo-plugin' ) );
+       /* translators: boo */ /* translators: this should get extracted too. */ /* some other comment */ $bar = g ( __( 'bubu', 'foo-plugin' ) );
       """
 
     When I run `wp i18n make-pot foo-plugin`
@@ -997,3 +998,267 @@ Feature: Generate a POT file of a WordPress plugin
       """
       msgid "Foo Plugin"
       """
+
+  Scenario: Extracts functions from JavaScript file
+    Given an empty foo-plugin directory
+    And a foo-plugin/foo-plugin.php file:
+      """
+      <?php
+      /**
+       * Plugin Name: Foo Plugin
+       */
+      """
+    And a foo-plugin/foo-plugin.js file:
+      """
+      __( '__', 'foo-plugin' );
+      _x( '_x', '_x_context', 'foo-plugin' );
+      _n( '_n_single', '_n_plural', number, 'foo-plugin' );
+      _nx( '_nx_single', '_nx_plural', number, '_nx_context', 'foo-plugin' );
+
+      __( 'wrong-domain', 'wrong-domain' );
+
+      __( 'Hello world' ); // translators: Greeting
+
+      // translators: Foo Bar Comment
+      __( 'Foo Bar', 'foo-plugin' );
+
+      // TrANslAtORs: Bar Baz Comment
+      __( 'Bar Baz', 'foo-plugin' );
+
+      // translators: Software name
+      const string = __( 'WordPress', 'foo-plugin' );
+
+      // translators: So much space
+
+      __( 'Spacey text', 'foo-plugin' );
+
+      /* translators: Long comment
+      spanning multiple
+      lines */
+      const string = __( 'Short text', 'foo-plugin' );
+
+      ReactDOM.render(
+        <h1>{__( 'Hello JSX', 'foo-plugin' )}</h1>,
+        document.getElementById('root')
+      );
+      """
+
+    When I run `wp i18n make-pot foo-plugin`
+    Then STDOUT should be:
+      """
+      Plugin file detected.
+      Success: POT file successfully generated!
+      """
+    And the foo-plugin/foo-plugin.pot file should exist
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid "__"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid "_x"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgctxt "_x_context"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid "_n_single"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid_plural "_n_plural"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid "_nx_single"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid_plural "_nx_plural"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgctxt "_nx_context"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid "Hello JSX"
+      """
+    And the foo-plugin/foo-plugin.pot file should not contain:
+      """
+      msgid "wrong-domain"
+      """
+
+  Scenario: Extract translator comments from JavaScript file
+    Given an empty foo-plugin directory
+    And a foo-plugin/foo-plugin.php file:
+      """
+      <?php
+      /**
+       * Plugin Name: Foo Plugin
+       */
+      """
+    And a foo-plugin/foo-plugin.js file:
+      """
+      /* translators: Translators 1! */
+      __( 'hello world', 'foo-plugin' );
+
+      /* Translators: Translators 2! */
+      const foo = __( 'foo', 'foo-plugin' );
+
+      /* translators: localized date and time format, see https://secure.php.net/date */
+      __( 'F j, Y g:i a', 'foo-plugin' );
+
+      // translators: let your ears fly!
+      __( 'on', 'foo-plugin' );
+
+      /*
+       * Translators: If there are characters in your language that are not supported
+       * by Lato, translate this to 'off'. Do not translate into your own language.
+       */
+      __( 'off', 'foo-plugin' );
+
+      /* translators: this should get extracted. */ let bar = __( 'baba', 'foo-plugin' );
+
+      /* translators: boo */ /* translators: this should get extracted too. */ /* some other comment */ let bar = g ( __( 'bubu', 'foo-plugin' ) );
+
+      /* translators: this is before the multiline call. */
+      var baz = __(
+        /* translators: this is inside the multiline call. */
+        'This is the original',
+        'foo-plugin'
+      );
+
+      ReactDOM.render(
+        /* translators: this is JSX */
+        <h1>{__( 'Hello JSX', 'foo-plugin' )}</h1>,
+        document.getElementById('root')
+      );
+      """
+
+    When I run `wp i18n make-pot foo-plugin`
+    Then STDOUT should be:
+      """
+      Plugin file detected.
+      Success: POT file successfully generated!
+      """
+    And the foo-plugin/foo-plugin.pot file should exist
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid "Foo Plugin"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: Translators 1!
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. Translators: Translators 2!
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      msgid "F j, Y g:i a"
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: localized date and time format, see https://secure.php.net/date
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: let your ears fly!
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. Translators: If there are characters in your language that are not supported by Lato, translate this to 'off'. Do not translate into your own language.
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: this should get extracted.
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: boo
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: this should get extracted too.
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: this is before the multiline call.
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: this is inside the multiline call.
+      """
+    And the foo-plugin/foo-plugin.pot file should contain:
+      """
+      #. translators: this is JSX
+      """
+
+  Scenario: Ignores any other text domain in JavaScript file
+    Given an empty foo-plugin directory
+    And a foo-plugin/foo-plugin.php file:
+      """
+      <?php
+      /**
+       * Plugin Name: Foo Plugin
+       */
+      """
+    And a foo-plugin/foo-plugin.js file:
+      """
+      __( 'Hello World', 'foo-plugin' );
+
+      __( 'Foo', 'bar' );
+
+      __( 'bar' );
+
+      ReactDOM.render(
+        <h1>{__( 'Hello JSX', 'baz' )}</h1>,
+        document.getElementById('root')
+      );
+      """
+
+    When I run `wp i18n make-pot foo-plugin foo-plugin.pot --domain=bar`
+    And the foo-plugin.pot file should contain:
+      """
+      msgid "Foo"
+      """
+    And the foo-plugin.pot file should not contain:
+      """
+      msgid "Hello World"
+      """
+    And the foo-plugin.pot file should not contain:
+      """
+      msgid "bar"
+      """
+     And the foo-plugin.pot file should not contain:
+      """
+      msgid "Hello JSX"
+      """
+
+  Scenario: Skips JavaScript file altogether
+    Given an empty foo-plugin directory
+    And a foo-plugin/foo-plugin.php file:
+      """
+      <?php
+      /**
+       * Plugin Name: Foo Plugin
+       */
+      """
+    And a foo-plugin/foo-plugin.js file:
+      """
+      __( 'Hello World', 'foo-plugin' );
+      """
+
+    When I run `wp i18n make-pot foo-plugin foo-plugin.pot --skip-js`
+    And the foo-plugin.pot file should contain:
+      """
+      msgid "Foo Plugin"
+      """
+    And the foo-plugin.pot file should not contain:
+      """
+      msgid "Hello World"
+      """
diff --git a/src/JsCodeExtractor.php b/src/JsCodeExtractor.php
new file mode 100644
index 00000000..32af1929
--- /dev/null
+++ b/src/JsCodeExtractor.php
@@ -0,0 +1,145 @@
+<?php
+
+namespace WP_CLI\I18n;
+
+use Gettext\Extractors\JsCode;
+use Gettext\Translations;
+use Peast\Syntax\Exception as PeastException;
+use RecursiveCallbackFilterIterator;
+use RecursiveDirectoryIterator;
+use RecursiveIteratorIterator;
+use DirectoryIterator;
+use WP_CLI;
+
+final class JsCodeExtractor extends JsCode {
+	private static $dir = '';
+
+	public static $options = [
+		'extractComments' => [ 'translators', 'Translators' ],
+		'constants'       => [],
+		'functions'       => [
+			'__'  => 'text_domain',
+			'_x'  => 'text_context_domain',
+			'_n'  => 'single_plural_number_domain',
+			'_nx' => 'single_plural_number_context_domain',
+		],
+	];
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public static function fromString( $string, Translations $translations, array $options = [] ) {
+		$options += static::$options;
+
+		$functions = new JsFunctionsScanner( $string );
+
+		$functions->enableCommentsExtraction( $options['extractComments'] );
+		$functions->saveGettextFunctions( $translations, $options );
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public static function fromFile( $file, Translations $translations, array $options = [] ) {
+		foreach ( static::getFiles( $file ) as $f ) {
+			// Make sure a relative file path is added as a comment.
+			$options['file'] = ltrim( str_replace( static::$dir, '', $f ), '/' );
+
+			$string = file_get_contents( $f );
+
+			if ( ! $string ) {
+				WP_CLI::debug(
+					sprintf(
+						'Could not load file %1s',
+						$f
+					)
+				);
+
+				continue;
+			}
+
+			try {
+				static::fromString( $string, $translations, $options );
+			} catch ( PeastException $e ) {
+				WP_CLI::debug(
+					sprintf(
+						'Could not parse file %1$s: %2$s (line %3$d, column %4$d)',
+						$options['file'],
+						$e->getMessage(),
+						$e->getPosition()->getLine(),
+						$e->getPosition()->getColumn()
+					)
+				);
+			}
+		}
+	}
+
+	/**
+	 * Recursively extracts the translations from a directory.
+	 *
+	 * @param string $dir Root path to start the recursive traversal in.
+	 * @param Translations $translations The translations instance to append the new translations.
+	 * @param array $options
+	 */
+	public static function fromDirectory( $dir, Translations $translations, array $options = [] ) {
+		static::$dir = $dir;
+
+		$files = static::getFilesFromDirectory( $dir, isset( $options['exclude'] ) ? $options['exclude'] : [] );
+
+		if ( ! empty( $files ) ) {
+			static::fromFile( $files, $translations, $options );
+		}
+
+		static::$dir = '';
+	}
+
+	/**
+	 * Recursively gets all PHP files within a directory.
+	 *
+	 * @param string $dir A path of a directory.
+	 * @param array $exclude List of files and directories to skip.
+	 *
+	 * @return array File list.
+	 */
+	private static function getFilesFromDirectory( $dir, array $exclude = [] ) {
+		$filtered_files = [];
+
+		$files = new RecursiveIteratorIterator(
+			new RecursiveCallbackFilterIterator(
+				new RecursiveDirectoryIterator( $dir, RecursiveDirectoryIterator::SKIP_DOTS ),
+				function ( $file, $key, $iterator ) use ( $exclude ) {
+					/** @var DirectoryIterator $file */
+					if ( in_array( $file->getBasename(), $exclude, true ) ) {
+						return false;
+					}
+
+					// Check for more complex paths, e.g. /some/sub/folder.
+					foreach( $exclude as $path_or_file ) {
+						if ( false !== mb_ereg( preg_quote( '/' . $path_or_file ) . '$', $file->getPathname() ) ) {
+							return false;
+						}
+					}
+
+					/** @var RecursiveCallbackFilterIterator $iterator */
+					if ( $iterator->hasChildren() ) {
+						return true;
+					}
+
+					return ( $file->isFile() && 'js' === $file->getExtension() );
+				}
+			),
+			RecursiveIteratorIterator::CHILD_FIRST
+		);
+
+		foreach ( $files as $file ) {
+			/** @var DirectoryIterator $file */
+			if ( ! $file->isFile() || 'js' !== $file->getExtension() ) {
+				continue;
+			}
+
+			$filtered_files[] = $file->getPathname();
+		}
+
+		return $filtered_files;
+	}
+}
diff --git a/src/JsFunctionsScanner.php b/src/JsFunctionsScanner.php
new file mode 100644
index 00000000..aef4676e
--- /dev/null
+++ b/src/JsFunctionsScanner.php
@@ -0,0 +1,171 @@
+<?php
+
+namespace WP_CLI\I18n;
+
+use Gettext\Translations;
+use Gettext\Utils\JsFunctionsScanner as GettextJsFunctionsScanner;
+use Gettext\Utils\ParsedComment;
+use Peast\Peast;
+use Peast\Syntax\Node;
+use Peast\Traverser;
+
+final class JsFunctionsScanner extends GettextJsFunctionsScanner {
+	/**
+	 * If not false, comments will be extracted.
+	 *
+	 * @var string|false|array
+	 */
+	private $extractComments = false;
+
+	/**
+	 * Enable extracting comments that start with a tag (if $tag is empty all the comments will be extracted).
+	 *
+	 * @param mixed $tag
+	 */
+	public function enableCommentsExtraction( $tag = '' ) {
+		$this->extractComments = $tag;
+	}
+
+	/**
+	 * Disable comments extraction.
+	 */
+	public function disableCommentsExtraction() {
+		$this->extractComments = false;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function saveGettextFunctions( Translations $translations, array $options ) {
+		$ast = Peast::latest( $this->code, [
+			'sourceType' => Peast::SOURCE_TYPE_MODULE,
+			'comments'   => false !== $this->extractComments,
+			'jsx'        => true,
+		] )->parse();
+
+		$traverser = new Traverser();
+
+		$all_comments = [];
+
+		/**
+		 * Traverse through JS code to find and extract gettext functions.
+		 *
+		 * Make sure translator comments in front of variable declarations
+		 * and inside nested call expressions are available when parsing the function call.
+		 */
+		$traverser->addFunction( function ( $node ) use ( &$translations, $options, &$all_comments ) {
+			$functions = $options['functions'];
+			$file      = $options['file'];
+
+			/** @var Node\Node $node */
+			foreach( $node->getLeadingComments() as $comment ) {
+				$all_comments[] = $comment;
+			}
+
+			/** @var Node\CallExpression $node */
+			if ( 'CallExpression' !== $node->getType() || 'Identifier' !== $node->getCallee()->getType() ) {
+				return;
+			}
+
+			/** @var Node\CallExpression $node */
+			foreach ( $node->getArguments() as $argument ) {
+				// Support nested function calls.
+				$argument->setLeadingComments( $argument->getLeadingComments() + $node->getLeadingComments() );
+			}
+
+			/** @var Node\Identifier $callee */
+			$callee = $node->getCallee();
+
+			if ( ! isset( $functions[ $callee->getName() ] ) ) {
+				return;
+			}
+
+			foreach( $callee->getLeadingComments() as $comment ) {
+				$all_comments[] = $comment;
+			}
+
+			$domain = $context = $original = $plural = null;
+			$args   = [];
+
+			/** @var Node\Node $argument */
+			foreach ( $node->getArguments() as $argument ) {
+				foreach( $argument->getLeadingComments() as $comment ) {
+					$all_comments[] = $comment;
+				}
+
+				if ( 'Identifier' === $argument->getType() ) {
+					$args[] = ''; // The value doesn't matter as it's unused.
+				}
+
+				if ( 'Literal' === $argument->getType() ) {
+					/** @var Node\Literal $argument */
+					$args[] = $argument->getValue();
+				}
+			}
+
+			switch ( $functions[ $callee->getName() ] ) {
+				case 'text_domain':
+				case 'gettext':
+					if ( ! isset( $args[1] ) ) {
+						break;
+					}
+
+					list( $original, $domain ) = $args;
+					break;
+
+				case 'text_context_domain':
+					if ( ! isset( $args[2] ) ) {
+						break;
+					}
+
+					list( $original, $context, $domain ) = $args;
+					break;
+
+				case 'single_plural_number_domain':
+					if ( ! isset( $args[3] ) ) {
+						break;
+					}
+
+					list( $original, $plural, $number, $domain ) = $args;
+					break;
+
+				case 'single_plural_number_context_domain':
+					if ( ! isset( $args[4] ) ) {
+						break;
+					}
+
+					list( $original, $plural, $number, $context, $domain ) = $args;
+					break;
+			}
+
+			if ( (string) $original !== '' && ( $domain === null || $domain === $translations->getDomain() ) ) {
+				$translation = $translations->insert( $context, $original, $plural );
+				$translation->addReference( $file, $node->getLocation()->getStart()->getLine() );
+
+				/** @var Node\Comment $comment */
+				foreach ( $all_comments as $comment ) {
+					if ( $node->getLocation()->getStart()->getLine() - $comment->getLocation()->getEnd()->getLine() > 1 ) {
+						continue;
+					}
+
+					if ( $node->getLocation()->getStart()->getColumn() < $comment->getLocation()->getStart()->getColumn() ) {
+						continue;
+					}
+
+					$parsed_comment = ParsedComment::create( $comment->getRawText(), $comment->getLocation()->getStart()->getLine() );
+					$prefixes       = array_filter( (array) $this->extractComments );
+
+					if ( $parsed_comment->checkPrefixes( $prefixes ) ) {
+						$translation->addExtractedComment( $parsed_comment->getComment() );
+					}
+				}
+
+				if ( isset( $parsed_comment ) ) {
+					$all_comments = [];
+				}
+			}
+		} );
+
+		$traverser->traverse( $ast );
+	}
+}
diff --git a/src/MakePotCommand.php b/src/MakePotCommand.php
index 8d98a2ca..43990d39 100644
--- a/src/MakePotCommand.php
+++ b/src/MakePotCommand.php
@@ -36,7 +36,7 @@ class MakePotCommand extends WP_CLI_Command {
 	/**
 	 * @var array
 	 */
-	protected $exclude = [ 'node_modules', '.git', '.svn', '.CVS', '.hg', 'vendor' ];
+	protected $exclude = [ 'node_modules', '.git', '.svn', '.CVS', '.hg', 'vendor', 'Gruntfile.js', 'webpack.config.js' ];
 
 	/**
 	 * @var string
@@ -48,9 +48,16 @@ class MakePotCommand extends WP_CLI_Command {
 	 */
 	protected $main_file_data = [];
 
+	/**
+	 * @var bool
+	 */
+	protected $skip_js = false;
+
 	/**
 	 * Create a POT file for a WordPress plugin or theme.
 	 *
+	 * Scans PHP and JavaScript files, as well as theme stylesheets for translatable strings.
+	 *
 	 * ## OPTIONS
 	 *
 	 * <source>
@@ -74,6 +81,9 @@ class MakePotCommand extends WP_CLI_Command {
 	 * By default, the following files and folders are ignored: node_modules, .git, .svn, .CVS, .hg, vendor.
 	 * Leading and trailing slashes are ignored, i.e. `/my/directory/` is the same as `my/directory`.
 	 *
+	 * [--skip-js]
+	 * : Skips JavaScript string extraction. Useful when this is done in another build step, e.g. through Babel.
+	 *
 	 * ## EXAMPLES
 	 *
 	 *     # Create a POT file for the WordPress plugin/theme in the current directory
@@ -82,8 +92,9 @@ class MakePotCommand extends WP_CLI_Command {
 	 * @when before_wp_load
 	 */
 	public function __invoke( $args, $assoc_args ) {
-		$this->source = realpath( $args[0] );
-		$this->slug   = Utils\get_flag_value( $assoc_args, 'slug', Utils\basename( $this->source ) );
+		$this->source  = realpath( $args[0] );
+		$this->slug    = Utils\get_flag_value( $assoc_args, 'slug', Utils\basename( $this->source ) );
+		$this->skip_js = Utils\get_flag_value( $assoc_args, 'skip-js', $this->skip_js );
 
 		if ( ! $this->source || ! is_dir( $this->source ) ) {
 			WP_CLI::error( 'Not a valid source directory!' );
@@ -123,6 +134,8 @@ public function __invoke( $args, $assoc_args ) {
 			}
 		}
 
+		WP_CLI::debug( sprintf( 'Destination: %s', $this->destination ), 'make-pot' );
+
 		if ( isset( $assoc_args['exclude'] ) ) {
 			$this->exclude = array_filter( array_merge( $this->exclude, explode( ',', $assoc_args['exclude'] ) ) );
 			$this->exclude = array_map(function($exclude) {
@@ -174,6 +187,7 @@ protected function retrieve_main_file_data() {
 			// Stop when we find a file with a valid Plugin Name header.
 			if ( ! empty( $plugin_data['Plugin Name'] ) ) {
 				WP_CLI::log( 'Plugin file detected.' );
+				WP_CLI::debug( sprintf( 'Plugin file: %s', $plugin_file ), 'make-pot' );
 
 				$this->main_file_data = $plugin_data;
 
@@ -257,12 +271,6 @@ protected function makepot( $domain ) {
 
 		$file_data = $this->get_main_file_data();
 
-		// Extract 'Template Name' headers in theme files.
-		WordPressCodeExtractor::fromDirectory( $this->source, $this->translations, [
-			'wpExtractTemplates' => isset( $file_data['Theme Name'] ),
-			'exclude'            => $this->exclude,
-		] );
-
 		unset( $file_data['Version'], $file_data['License'], $file_data['Domain Path'] );
 
 		// Set entries from main file data.
@@ -282,6 +290,20 @@ protected function makepot( $domain ) {
 			$this->translations[] = $translation;
 		}
 
+		try {
+			PhpCodeExtractor::fromDirectory( $this->source, $this->translations, [
+				// Extract 'Template Name' headers in theme files.
+				'wpExtractTemplates' => isset( $file_data['Theme Name'] ),
+				'exclude'            => $this->exclude,
+			] );
+
+			if ( ! $this->skip_js ) {
+				JsCodeExtractor::fromDirectory( $this->source, $this->translations );
+			}
+		} catch ( \Exception $e ) {
+			WP_CLI::error( $e->getMessage() );
+		}
+
 		foreach( $this->translations as $translation ) {
 			if ( ! $translation->hasExtractedComments() ) {
 				continue;
diff --git a/src/WordPressCodeExtractor.php b/src/PhpCodeExtractor.php
similarity index 64%
rename from src/WordPressCodeExtractor.php
rename to src/PhpCodeExtractor.php
index 2b4686e8..8b91e02c 100644
--- a/src/WordPressCodeExtractor.php
+++ b/src/PhpCodeExtractor.php
@@ -8,11 +8,11 @@
 use RecursiveCallbackFilterIterator;
 use RecursiveDirectoryIterator;
 use RecursiveIteratorIterator;
-use SplFileInfo;
+use DirectoryIterator;
 use WP_CLI;
 
-class WordPressCodeExtractor extends PhpCode {
-	protected static $dir = '';
+final class PhpCodeExtractor extends PhpCode {
+	private static $dir = '';
 
 	public static $options = [
 		'extractComments' => [ 'translators', 'Translators' ],
@@ -50,12 +50,9 @@ class WordPressCodeExtractor extends PhpCode {
 	public static function fromString( $string, Translations $translations, array $options = [] ) {
 		$options += static::$options;
 
-		$functions = new WordPressFunctionsScanner( $string );
-
-		if ( $options['extractComments'] !== false ) {
-			$functions->enableCommentsExtraction( $options['extractComments'] );
-		}
+		$functions = new PhpFunctionsScanner( $string );
 
+		$functions->enableCommentsExtraction( $options['extractComments'] );
 		$functions->saveGettextFunctions( $translations, $options );
 	}
 
@@ -63,13 +60,24 @@ public static function fromString( $string, Translations $translations, array $o
 	 * {@inheritdoc}
 	 */
 	public static function fromFile( $file, Translations $translations, array $options = [] ) {
-		foreach ( self::getFiles( $file ) as $f ) {
+		foreach ( static::getFiles( $file ) as $f ) {
 			// Make sure a relative file path is added as a comment.
 			$options['file'] = ltrim( str_replace( static::$dir, '', $f ), '/' );
 
-			$string = self::readFile( $f );
+			$string = file_get_contents( $f );
+
+			if ( ! $string ) {
+				WP_CLI::debug(
+					sprintf(
+						'Could not load file %1s',
+						$f
+					)
+				);
+
+				continue;
+			}
 
-			if ( $options['wpExtractTemplates'] ) {
+			if ( ! empty ( $options['wpExtractTemplates'] ) ) {
 				$headers = MakePotCommand::get_file_data_from_string( $string, [ 'Template Name' => 'Template Name' ] );
 
 				if ( ! empty( $headers[ 'Template Name'])) {
@@ -96,12 +104,8 @@ public static function fromDirectory( $dir, Translations $translations, array $o
 
 		$files = static::getFilesFromDirectory( $dir, isset( $options['exclude'] ) ? $options['exclude'] : [] );
 
-		try {
-			if ( ! empty( $files ) ) {
-				static::fromFile( $files, $translations, $options );
-			}
-		} catch ( \Exception $e ) {
-			WP_CLI::error( $e->getMessage() );
+		if ( ! empty( $files ) ) {
+			static::fromFile( $files, $translations, $options );
 		}
 
 		static::$dir = '';
@@ -115,45 +119,43 @@ public static function fromDirectory( $dir, Translations $translations, array $o
 	 *
 	 * @return array File list.
 	 */
-	protected static function getFilesFromDirectory( $dir, array $exclude = [] ) {
+	private static function getFilesFromDirectory( $dir, array $exclude = [] ) {
 		$filtered_files = [];
 
-		try {
-			$files = new RecursiveIteratorIterator(
-				new RecursiveCallbackFilterIterator(
-					new RecursiveDirectoryIterator( $dir, RecursiveDirectoryIterator::SKIP_DOTS ),
-					function ( $file, $key, $iterator ) use ( $exclude ) {
-						/** @var SplFileInfo $file */
-						if ( in_array( $file->getBasename(), $exclude, true ) ) {
-							return false;
-						}
-
-						// Check for more complex paths, e.g. /some/sub/folder.
-						foreach( $exclude as $path_or_file ) {
-							if ( false !== mb_ereg( preg_quote( '/' . $path_or_file ) . '$', $file->getPathname() ) ) {
-								return false;
-							}
-						}
+		$files = new RecursiveIteratorIterator(
+			new RecursiveCallbackFilterIterator(
+				new RecursiveDirectoryIterator( $dir, RecursiveDirectoryIterator::SKIP_DOTS ),
+				function ( $file, $key, $iterator ) use ( $exclude ) {
+					/** @var DirectoryIterator $file */
+					if ( in_array( $file->getBasename(), $exclude, true ) ) {
+						return false;
+					}
 
-						/** @var RecursiveCallbackFilterIterator $iterator */
-						if ( $iterator->hasChildren() ) {
-							return true;
+					// Check for more complex paths, e.g. /some/sub/folder.
+					foreach( $exclude as $path_or_file ) {
+						if ( false !== mb_ereg( preg_quote( '/' . $path_or_file ) . '$', $file->getPathname() ) ) {
+							return false;
 						}
+					}
 
-						return ( $file->isFile() && 'php' === $file->getExtension() );
+					/** @var RecursiveCallbackFilterIterator $iterator */
+					if ( $iterator->hasChildren() ) {
+						return true;
 					}
-				),
-				RecursiveIteratorIterator::CHILD_FIRST
-			);
-
-			/** @var SplFileInfo $file */
-			foreach ( $files as $file ) {
-				if ( $file->isFile() ) {
-					$filtered_files[] = $file->getPathname();
+
+					return ( $file->isFile() && 'php' === $file->getExtension() );
 				}
+			),
+			RecursiveIteratorIterator::CHILD_FIRST
+		);
+
+		foreach ( $files as $file ) {
+			/** @var DirectoryIterator $file */
+			if ( ! $file->isFile() || 'php' !== $file->getExtension() ) {
+				continue;
 			}
-		} catch ( \Exception $e ) {
-			WP_CLI::error( $e->getMessage() );
+
+			$filtered_files[] = $file->getPathname();
 		}
 
 		return $filtered_files;
diff --git a/src/WordPressFunctionsScanner.php b/src/PhpFunctionsScanner.php
similarity index 93%
rename from src/WordPressFunctionsScanner.php
rename to src/PhpFunctionsScanner.php
index b98d56dd..16e92f5f 100644
--- a/src/WordPressFunctionsScanner.php
+++ b/src/PhpFunctionsScanner.php
@@ -3,9 +3,9 @@
 namespace WP_CLI\I18n;
 
 use Gettext\Translations;
-use Gettext\Utils\PhpFunctionsScanner;
+use Gettext\Utils\PhpFunctionsScanner as GettextPhpFunctionsScanner;
 
-class WordPressFunctionsScanner extends PhpFunctionsScanner {
+final class PhpFunctionsScanner extends GettextPhpFunctionsScanner {
 	/**
 	 * {@inheritdoc}
 	 */
@@ -77,7 +77,6 @@ public function saveGettextFunctions( Translations $translations, array $options
 					\WP_CLI::error( sprintf( "Internal error: unknown function map '%s' for '%s'.", $functions[ $name ], $name ) );
 			}
 
-			// Todo: Require a domain?
 			if ( (string) $original !== '' && ( $domain === null || $domain === $translations->getDomain() ) ) {
 				$translation = $translations->insert( $context, $original, $plural );
 				$translation = $translation->addReference( $file, $line );