AEM JavaScript Use-API

Tips and resources for using AEM’s Sightly / HTL JavaScript Use-API for writing server-side JavaScript. The AEM JavaScript Use-API ResourceUtils page contains examples for using ResourceUtils and functions.


AEM uses Rhino to compile server-side JavaScript into Java. All of the regular Java libraries are available by using the class path in the server-side JavaScript. Since the server-side JavaScript is slower than using Java, it’s best to use when the components will be cached in the dispatcher.


Navigate to the equipment page in author mode, e.g., /editor.html/content/we-retail/us/en/equipment.html. Scroll down to the Featured Products panel. Notice the descriptions below the product names are all lowercase. e.g., footwear, helmet, shirt …

Let’s create a server-side JavaScript file to title case these descriptions.

In crx/de, e.g., http://localhost:4502/crx/de, expand /apps/weretail/components/content/productgrid.

Right-click item and select Create > Create File

Name the file item.js and add the following JavaScript Use-API code:

"use strict";

use( function() {

  var data = {};

   * `this.item` is the item parameter object
   * passed from the HTL template
  data.description = toTitleCase(this.item.description);

  function toTitleCase(str) {
    var _str = new String(str);
    return _str.replace(/(^|\s)[a-z]/g, function(chr){ return chr.toUpperCase() });

  return data;


Edit /apps/weretail/components/content/productgrid/item/item.html adding a sly element to use the server-side JavaScript file and pass it the item data. e.g.,


<li class="foundation-list-item"


    <sly data-sly-use.product="${'item.js' @ item=item}" />





Reload the /editor.html/content/we-retail/us/en/equipment.html page in author mode and the descriptions should now be title cased.

AEM Sample We Retail | Product Grid with item descriptions title cased

Component Properties

To access the properties of a page or component, refer to the following examples.

Using POJO

var pageTitle =["jcr:title"];

// all three of these component property examples work
var txtTest1 =["text"];
var txtTest2 =["text"];
var txtTest3 = properties["text"];

Using the properties JcrPropertyMap

var pageTitle ="jcr:title");

If you want to specify a value to use when the property does not exist, you can after the property name. e.g.,

var title = properties.get("myproperty", '');


As we saw in the example above with <sly data-sly-use.product="${'item.js' @ item=item}" />, objects that are not properties of the respective component can be passed to the Use-API using parameters. The next part contains another example of this.

Java Classes

Java classes can be accessed directly with the classpath. e.g.,

var beer = "lager";
var wine = "pinot grigio";

var difference = org.apache.commons.lang.StringUtils.difference(beer, wine);

Type Casting

Using native JavaScript methods, e.g., toLowerCase() on objects that do not originate within the script need to be cast. For example, cast the java.lang.String to new String(); e.g.,

var name = new String(;

Debugging / Logging

Debugging is essential to development, especially when trying to learn what JavaScript patterns, variables, etc. can be utilized within the Use-API. Unfortunately, debugging with breakpoints, etc. is not supported and we’re relegated to using logs and output strings.

Custom Log File

Navigate to the Web Console and select Sling: Log Support. e.g., http://localhost:4502/system/console/slinglog

  1. Select Add new Logger,

  2. Select DEBUG for the log level, e.g., Log Level: DEBUG;

  3. Enter a log file path, e.g., Log File: logs/debug.log

  4. Enter a path for the Logger, e.g., apps

  5. Select the Save button

Adobe Experience Manager Web Console Log Support | Add new Logger

Create a server-side JavaScript file to test the logger.

In crx/de, e.g., http://localhost:4502/crx/de

expand apps/weretail/components/structure right-click page and select Create > Create File

name the file, e.g., example.js and add the following Use-API code:

"use strict";

use( function() {

  log.debug('### TESTING');


Edit /apps/weretail/components/structure/page/body.html and add a sly element to use the server-side JavaScript file. e.g.,

<div class="container">

    <sly data-sly-use.test="${'example.js'}"></sly>

Load the URL to test the file, for example, http://localhost:4502/content/we-retail/us/en.html

Read the log file

This example shows how to tail the log in a terminal session. Use tail to monitor log files in real time. The -n300 argument show the last 300 lines. The default is only 10 lines.

cd /opt/aem/author/crx-quickstart/logs

tail -n300 -f debug.log

Use the tail command with the -f argument to follow the content of a file. Use the -F argument to follow the creation of a new log.

This example shows how to return only log entries for a specific Use-API class.

tail -f debug.log | grep {Use Class name}

If you want to use the a web browser to view the log file, open the WebTail endpoint to read the last 1000 lines of the custom log file, for example:



Part 1 of 4 in the AEM JavaScript Use-API series.

AEM JavaScript Use-API String Multi JSON

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