feat: modernize Problem Block JS to ES6+ syntax

[irfanuddinahmad]

Summary

Closes openedx/public-engineering#438

Converts all three capa JavaScript files to ES6+ syntax and removes the legacy imports-loader workarounds.

Source file changes

• display.js — Removed CoffeeScript IIFE wrapper; added import $ from 'jquery'; replaced 28 prototype method-binding boilerplate blocks with clean .bind(this) calls; removed Array.indexOf polyfill in favour of Array.prototype.includes(); converted all var → const/let; template literals throughout; explicit window.Problem = Problem + ES6 export.
• imageinput.js — Rewritten as an ES6 class ImageInput with import $ from 'jquery'; const/let; template literals; window.ImageInput = ImageInput + ES6 export.
• schematic.js — Added import $ from 'jquery'; module-level var cktsim/var schematic → const; added named + default exports; kept window.update_schematics assignment for backwards compatibility with callers that reference it as a global.

Spec file changes

• spec/imageinput_spec.js — Rewritten to ES6: import ImageInput, const/let, template literals, no IIFE wrapper.
• spec/display_spec.js — Added import Problem from '../static/js/display.js' to make the dependency explicit.

Build config changes

• webpack.config.js — Removed imports-loader (this=>window) entries for display.js, imageinput.js, and schematic.js (no longer needed now that the files use proper ES6 imports/exports). Updated babel-loader exclude regex so these three files are now Babel-processed.

Test plan

• npm run build passes with no errors
• npm test — capa Karma tests (display_spec.js, imageinput_spec.js) pass

Local Testing

Prerequisites

• A local Tutor instance running (tested on Tutor v21 / Indigo)
• Admin credentials for Studio and LMS

Setup: add problem blocks to a course

1. Open Studio and log in (http://studio.local.openedx.io)

2. Open any course (or create one)

3. In the course outline, navigate to a Section → Subsection and click + New Unit

4. Inside the unit, click + New Component → Problem and add one of each type below:

   Problem type	JS file exercised
   Multiple Choice (default template)	display.js
   Checkboxes	display.js
   Image Input	imageinput.js
   Circuit Schematic Builder	schematic.js

   Note: For Checkboxes, Image Input, and Circuit Schematic, use Edit → Advanced editor and paste raw OLX — the authoring MFE's visual editor may not support these types.

5. Click Publish in the sidebar

6. Enroll your user in the course if not already enrolled

Verification

Open the unit in the learner view (http://apps.local.openedx.io/learning/course/<course-id>/home) and for each problem type:

• Open DevTools → Console — no new JS errors on load (JQMIGRATE deprecation warnings from lms-main_vendor.js are pre-existing and unrelated)
• Multiple Choice / Checkboxes — select an answer and click Submit; confirm correct/incorrect feedback appears and the score updates
• Image Input — click on the image to place a marker; confirm the coordinate is captured and submission works
• Circuit Schematic — confirm the schematic editor renders and is interactive in the browser (server-side grading requires codejail, which may not be configured in all local setups)
• In DevTools → Sources, search for ProblemBlockDisplay → open the bundle → search for ImageInput; confirm the ES6 class ImageInput declaration is present, confirming the new bundle is served

🤖 Generated with Claude Code

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[salman2013]

@irfanuddinahmad Please do some manual testing on problem xblock as there are changes in js files so to make sure everything is working as expected.

[irfanuddinahmad]

@irfanuddinahmad Please do some manual testing on problem xblock as there are changes in js files so to make sure everything is working as expected.

@salman2013 Done. Tests and Screenshots posted above.