How to Optimize JavaScript Code with Code-Graph-RAG: A Complete Guide

Code-Graph-RAG optimizes JavaScript by parsing source files into a Memgraph knowledge graph via Tree-sitter, enabling LLM-driven analysis to suggest AST-based refactors that preserve cross-module dependencies and call-graph integrity.

Code-Graph-RAG (vitali87/code-graph-rag) is an open-source engine that builds language-agnostic knowledge graphs from multi-language codebases to power intelligent refactoring. When you optimize JavaScript code with this tool, it queries the stored Abstract Syntax Tree (AST) representations rather than raw text, allowing it to suggest performance improvements that account for import chains, class hierarchies, and function call relationships.

Understanding the Code-Graph-RAG Architecture

The system constructs a queryable graph of your codebase using a three-layer pipeline defined in docs/architecture/overview.md.

Tree-sitter parsing ingests JavaScript files and extracts entities—functions, classes, modules, imports—into structured nodes. These nodes and their relationships (calls, extends, imports) are persisted in Memgraph according to the schema documented in docs/architecture/graph-schema.md. Language identifiers such as "javascript" are defined in codebase_rag/workspaces/constants.py, allowing the optimizer to target specific subgraphs.

This graph structure enables the system to trace side effects across file boundaries, a capability that text-based regular expressions cannot replicate.

The Five-Stage JavaScript Optimization Pipeline

The optimization workflow implemented in codebase_rag/cli.py follows a rigorous five-stage process:

1. Graph-Driven Analysis

The engine queries the JavaScript subgraph in Memgraph to locate functions, methods, and modules exhibiting known anti-patterns. It identifies excessive memory allocations, synchronous I/O bottlenecks, and duplicate code blocks by analyzing AST node attributes stored as graph properties.

2. Pattern Recognition

An LLM orchestrator—configured in codebase_rag/workspaces/models.py—examines the AST nodes in situ. It detects performance-critical constructs such as nested loops, heavy string concatenation in hot paths, and unnecessary Promise chains that could be parallelized.

3. Best-Practice Application

The system generates language-specific recommendations grounded in the ES2022+ specification. Because suggestions reference exact symbol locations within the graph, they include precise file paths and line numbers, ensuring that advice like "convert to async/await" or "adopt immutable data structures" is contextually anchored to your specific codebase structure.

4. Interactive Approval

Each proposed optimization is presented through the CLI for explicit user consent. This step prevents unintended breaking changes by requiring [y/n] confirmation before any mutation occurs, as detailed in the usage guide at docs/guide/code-optimization.md.

5. Patch Generation and Execution

Upon approval, the tool computes a minimal AST-based diff rather than a text-based search-and-replace. The patch updates the repository files and simultaneously synchronizes the changes back into the Memgraph knowledge graph, ensuring that subsequent queries reflect the newly optimized code structure.

CLI Commands for JavaScript Optimization

The cgr optimize javascript command exposes several flags to control the optimization process:

# Basic JavaScript optimization using the default LLM

cgr optimize javascript --repo-path /path/to/your/frontend

# Apply custom style guidelines during optimization

cgr optimize javascript \
    --repo-path /path/to/your/frontend \
    --reference-document ./js_best_practices.md

# Specify a particular LLM orchestrator for the analysis

cgr optimize javascript \
    --repo-path /path/to/your/frontend \
    --orchestrator google:gemini-3.6-flash

# Adjust Memgraph batch size for large monorepos

cgr optimize javascript \
    --repo-path /path/to/your/frontend \
    --batch-size 8000

During execution, the CLI displays interactive prompts:

Optimization Suggestion #1:
  File: src/utils/api.js
  Issue: Repeated use of `new Promise` inside a loop
  Suggestion: Convert the loop to `Promise.all` with async/await for parallelism
  [y/n] Do you approve this optimisation?

After confirmation, the terminal renders the exact diff before applying it to disk.

How the Knowledge Graph Enables Safe Refactoring

Because Code-Graph-RAG operates on the graph abstraction rather than raw text, it safely handles complex refactoring scenarios that span module boundaries. When you optimize JavaScript code, the system tracks call-graph impacts, automatically updating import and export statements to reflect moved or renamed symbols.

This graph-awareness prevents the stale reference errors common in traditional find-and-replace workflows. The tool understands that renaming a default export in utils/helpers.js requires corresponding updates in every file that imports from that module, and it batches these changes into a single atomic transaction.

Summary

• Graph-based analysis parses JavaScript into a queryable Memgraph database using Tree-sitter, capturing functions, classes, and dependencies as interconnected nodes.
• Five-stage pipeline progresses from anti-pattern detection through LLM-powered pattern recognition to interactive, AST-based patch generation.
• CLI flexibility supports custom orchestrators, reference documents, and batch tuning via flags defined in codebase_rag/cli.py.
• Safe refactoring preserves cross-module integrity by tracking import/export relationships and call-graph dependencies during optimization.

Frequently Asked Questions

How does Code-Graph-RAG differ from traditional linters like ESLint?

While ESLint applies static rules to text, Code-Graph-RAG queries a persistent knowledge graph of your AST to understand cross-file relationships. This allows it to suggest architectural refactors—such as consolidating duplicate utilities across packages—that require holistic codebase awareness rather than single-file pattern matching.

Can I use Code-Graph-RAG with other languages in the same repository?

Yes. The system is language-agnostic, storing entities for JavaScript, Python, Go, and other supported languages in the same Memgraph instance. You can run cgr optimize targeting different languages sequentially, and the graph maintains cross-language references where bindings exist.

Is the optimization process safe for production codebases?

The tool requires explicit approval for every change via interactive CLI prompts. Because it generates AST-based diffs rather than text replacements, it eliminates the risk of regex-induced syntax errors. However, as with any automated refactoring, you should run your test suite after applying patches.

Which LLM orchestrators are compatible with the optimizer?

The system supports multiple backends configurable via the --orchestrator flag, including google:gemini-3.6-flash and other providers defined in the orchestration logic of codebase_rag/workspaces/models.py. You can extend support for additional LLMs by implementing the provider interface in that module.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}