diff --git a/defaults.yml b/defaults.yml
index 507c204c..3bbf5c7c 100644
--- a/defaults.yml
+++ b/defaults.yml
@@ -302,3 +302,21 @@ styleguide:
   root: 'styleguide'
   # Command to compile the style guide assets, for use during the build and artifact steps.
   command: 'yarn default'
+
+# Configuration for linting custom javascript.
+#
+# Update these properties to reflect the directories and extensions used for
+# your project's custom javascript.
+# @see https://eslint.org/docs/latest/use/core-concepts
+eslint:
+  # Run eslint on custom modules AND themes, this must be a single value.
+  # @see: https://eslint.org/docs/latest/use/command-line-interface#run-the-cli
+  #
+  # If you need multiple directories that don't match a single pattern, you
+  # may need to add multiple config values here and add a for loop to the build
+  # target for eslint.
+  directory: "${drupal.root}/**/custom/"
+  # Run eslint on files with .es6.js extension.
+  # This can be a comma separated list.
+  # @see: https://eslint.org/docs/latest/use/command-line-interface#--ext
+  extensions: ".es6.js"
diff --git a/defaults/install/build.xml b/defaults/install/build.xml
index ff91ef1e..dbee1d35 100644
--- a/defaults/install/build.xml
+++ b/defaults/install/build.xml
@@ -128,6 +128,9 @@
         <!-- Run Drupal Check. -->
         <foreach list="${drupal-check.directories}" param="drupal-check.dir" target="drupal-check" />
 
+        <!-- Run eslint -->
+        <phingcall target="eslint" />
+
         <!-- Ensure the composer.lock file is up to date -->
         <exec command="composer validate --no-check-all --no-check-publish" logoutput="true" checkreturn="true" />
     </target>
@@ -143,6 +146,13 @@
         <exec command="${drupal-check.command}" logoutput="true" checkreturn="true" />
     </target>
 
+    <!-- Target: eslint -->
+    <target name="eslint" depends="install-node-dependencies">
+        <!-- Lint custom module and theme (by default) javascript. -->
+        <echo msg="$> yarn run eslint --ext ${eslint.extensions} ${eslint.directory}" />
+        <exec command="yarn run eslint --fix-dry-run --ext ${eslint.extensions} --resolve-plugins-relative-to ${drupal.root}/core --no-error-on-unmatched-pattern ${eslint.directory}" logoutput="true" checkreturn="true" />
+    </target>
+
 
     <!-- Target: code-fix -->
     <target name="code-fix" description="Run the automated code fixer.">
@@ -151,6 +161,32 @@
         <exec command="vendor/bin/phpcbf" logoutput="true" checkreturn="false" />
     </target>
 
+    <!-- Target: install-node-dependencies -->
+    <target name="install-node-dependencies" depends="" description="Install project, core, and custom module node dependencies">
+        <echo msg="Seeing if project npm packages are installed and at the expected version." />
+        <exec command="yarn install --check-files --verbose" returnProperty="project_dependencies"  logoutput="true" />
+        <if>
+            <not>
+                <equals arg1="${project_dependencies}" arg2="0" />
+            </not>
+            <then>
+                <echo msg="Install project node dependencies to get eslint libraries." />
+                <exec dir="${drupal.root}/.." command="yarn install" logoutput="true" />
+            </then>
+        </if>
+        <echo msg="Seeing if Drupal core npm packages are installed and at the expected version." />
+        <exec dir="${drupal.root}/core" command="yarn install --check-files --verbose" returnProperty="core_dependencies"  logoutput="true" />
+        <if>
+            <not>
+                <equals arg1="${core_dependencies}" arg2="0" />
+            </not>
+            <then>
+                <echo msg="Install Core node dependencies to get eslint libraries." />
+                <exec dir="${drupal.root}/core" command="yarn install" logoutput="true" checkreturn="true" />
+            </then>
+        </if>
+    </target>
+
 
     <!-- Target: artifact -->
     <target name="artifact" description="Build and deploy the application.">
diff --git a/defaults/install/phpcs.xml b/defaults/install/phpcs.xml
index 0fe430df..cacd6a09 100644
--- a/defaults/install/phpcs.xml
+++ b/defaults/install/phpcs.xml
@@ -16,7 +16,7 @@
   <config name="ignore_errors_on_exit" value="0" />
 
   <!-- Set extensions to scan. -->
-  <arg name="extensions" value="php,module,inc,install,test,profile,theme,info,yml,css,js"/>
+  <arg name="extensions" value="php,module,inc,install,test,profile,theme,info,yml,css"/>
 
   <!-- Use colors in output. -->
   <arg name="colors"/>