Code Review

All of the general standards of code review apply equally to JavaScript. See Code Contributions and Review for general guidance on code review. This document summarizes points to keep in mind specifically when reviewing JavaScript in CommCare HQ.


Make any user-facing language as clear as possible.

  • Proofread it.

  • Limit jargon and overly technical language (using pre-existing HQ terms is okay)

  • Don’t let internal names bleed into user-facing content

    • “Lookup tables” not “fixtures”

    • “Web apps” not “cloudcare”

    • “Mobile worker” not “mobile user” or “CommCare User”

    • etc.


  • All user-facing text should be translated with gettext, which is globally available in HQ JavaScript.

  • Strings that contain variables should use _.template as described in the translations docs.

Time Zones

  • All user-facing dates and times should be displayed in a time zone that will make sense for the user. Look at usage of UserTime and more generally at corehq.util.timezones.


  • Use <%- ... %> in Underscore templates to HTML escape values.

  • Use DomPurify to HTML escape user input that will be displayed, but not in a template.

Delays and Errors

  • Any potentially long-running requests, including all AJAX requests, should use a spinner or similar indicator.

    • jQuery: Use disableButton to disable & add a spinner, then enableButton when the request succeeds or fails.

    • Knockout: These usally need custom-but-usually-short disable/spinner code, probably using a boolean observable and a disable binding in the HTML.

    • There may not be spinner/disable code if there’s an HTML form and it uses the disable-on-submit class.

  • Any AJAX requests should have an error callback.

    • This usually doesn’t need to be fancy, just to display a generic “Try again”-type error near the action that was taken. Most requests aren’t error-prone, this is typically just to defend against generic platform errors like the user getting logged out.

Coding Standards

Again, standards in JavaScript are largely the same as in Python. However, there are a few issues that are either specific to JavaScript or more frequently arise in it:

  • Naming. JavaScript is often messy because it sometimes uses server naming conventions, which are different, for server data. Push the author to leave the code better than they found it. Don’t allow the same identifier to be used with different capitalizations, e.g., firstName and first_name in the same file. Find a synonym for one of them.

  • JavaScript should be enclosed in modules and those modules should explicitly declare dependencies, as in the first code block here. Exceptions are app manager, reports, and web apps.

  • Avoid long lists of params. Prefer kwargs-style objects and use assert_properties to verify they contain the expected options.

  • Make sure any js access of initial page data is guaranteed not to happen until the page is fully loaded. Not doing so risks a race condition that will break the page. Keep an eye out that any new initial page data accessed in js is made available in HTML (usually not an issue unless the author didn’t test at all).

  • Prefer knockout to jQuery. Avoid mixing knockout and jQuery. Recall that you don’t have to solve the author’s problems. It’s enough to say, “This is a lot of jQuery, have you considered making a knockout model?”