js-modern

name	js-modern
description	Write modern JavaScript and TypeScript — ES6+ features, async/await, modules, destructuring, optional chaining, TypeScript types. Covers SFCC server-side JS (CommonJS, limited ES6), PWA Kit (full modern JS/TS), and LWC JavaScript (Lightning Locker constraints). Use when writing JavaScript for Salesforce Commerce.
allowed-tools	Read, Write, Edit, Bash, Grep, Glob, WebSearch, WebFetch

js-modern

Write modern JavaScript and TypeScript for Salesforce Commerce platforms.

Before Writing Code

Always fetch the latest official documentation BEFORE writing JavaScript:

• MDN JavaScript Reference: WebSearch "MDN JavaScript reference ES6 2026" and WebFetch official docs
• TypeScript Documentation: WebSearch "TypeScript handbook 2026" and WebFetch official docs
• Platform-Specific Docs: WebSearch for "Salesforce B2C Commerce server-side JavaScript API 2026" (SFCC), "PWA Kit JavaScript TypeScript 2026" (PWA Kit), or "Lightning Web Components JavaScript 2026" (LWC)

This ensures you're using the latest syntax, APIs, and best practices for each platform.

Conceptual Architecture

Platform Runtime Constraints

This is the most critical concept. Three Salesforce Commerce platforms have fundamentally different JavaScript runtimes:

Constraint	SFCC Server-Side	PWA Kit	LWC (B2B)
Engine	Rhino (Java-based)	Node.js + V8	Browser (V8/SpiderMonkey)
Module system	CommonJS (require)	ES Modules (import)	ES Modules (import)
async/await	Not supported	Fully supported	Fully supported
Promises	Not supported	Fully supported	Fully supported
Template literals	Limited contexts	Fully supported	Fully supported
Arrow functions	Supported	Supported	Supported
Destructuring	Supported	Supported	Supported
Optional chaining	Not supported	Supported	Supported
Classes	Not supported	Supported	Required (extends LightningElement)
Decorators	Not applicable	Not applicable	Required (@api, @track, @wire)
DOM access	Not applicable	Standard DOM	Shadow DOM only (Locker/LWS)

SFCC Server-Side JavaScript

The Rhino engine imposes strict limitations. Every SFCC script must account for these:

• Use var or let/const (recent versions) -- verify against your instance
• No async/await, no Promise -- all I/O is synchronous
• No ES modules -- use require('dw/...') and module.exports
• Access platform APIs via dw.* namespace (e.g., dw/catalog/ProductMgr)
• Use module.superModule for cartridge overlay inheritance

// Pattern: SFCC module import
var ProductMgr = require('dw/catalog/ProductMgr');
// Fetch live docs for dw.* API signatures

// Pattern: module.superModule extension
var base = module.superModule;
// Fetch live docs for superModule behavior

PWA Kit JavaScript/TypeScript

Full modern JavaScript and TypeScript are available:

Feature	Stack
React	17+ with hooks
TypeScript	Full support, recommended
Node.js SSR	Server-side rendering
Commerce SDK	commerce-sdk-isomorphic
Bundler	Webpack with code splitting

// Pattern: PWA Kit component with Commerce SDK
// Fetch live docs for useProducts hook API
import { useProducts } from '@salesforce/commerce-sdk-react';

LWC JavaScript Constraints

LWC uses modern ES modules but enforces security boundaries:

Allowed	Not Allowed
ES modules (import/export)	Direct window/document manipulation
async/await, Promises	eval(), Function() constructor
Template literals, destructuring	Third-party DOM libraries (jQuery)
@api, @track, @wire decorators	setTimeout(string)
this.template.querySelector()	document.getElementById()
NavigationMixin	window.location = ...

// Pattern: LWC component skeleton
// Fetch live docs for decorator behavior
import { LightningElement, api, wire } from 'lwc';

Module Systems Comparison

System	Syntax	Platform
CommonJS	require() / module.exports	SFCC server-side
ES Modules	import / export	PWA Kit, LWC
SFCC Overlay	module.superModule	SFCC cartridge extension
SFCC Wildcard	require('*/cartridge/...')	Cross-cartridge resolution

Best Practices

Platform Adaptation

• Always verify which JS features your target platform supports before coding
• SFCC: Use CommonJS, avoid async/await, leverage dw.* API
• PWA Kit: Use full modern JS/TS, React hooks, Commerce SDK
• LWC: Use ES modules, decorators, respect Lightning Web Security

Code Quality

• Use const by default, let when reassignment is needed, never var (except SFCC if required)
• Prefer modern array methods (map, filter, reduce) over imperative loops
• Use optional chaining (?.) and nullish coalescing (??) where supported
• Destructure to extract values for cleaner, more readable code

TypeScript (PWA Kit)

• Use TypeScript for type safety and better IDE support
• Leverage Commerce SDK types for API responses
• Use Partial<T>, Pick<T>, Omit<T> for flexible type definitions

Fetch MDN, TypeScript handbook, and platform-specific Salesforce docs for exact syntax support and API signatures before implementing.