worstcase

Automatic time and space complexity analyzer for JavaScript/TypeScript code

Overview

Ever wondered if your JS/TS code is secretly harboring a performance monster? worstcase is your solution! This powerful tool automatically analyzes your JS/TS code and computes approximate Big O complexity for both time and space through static code analysis.

Motivation

The motivation is simple yet ambitious: to bring algorithmic analysis directly into the development workflow. Instead of manually reasoning through loops and recursive calls, or waiting for performance issues to surface in production, this analyzer examines your code structure and provides instant complexity estimates. It's like having a computer science professor looking over your shoulder, but one who never gets tired and works at the speed of light.

Features

• Automated Complexity Analysis: Computes Big O notation for time and space complexity
• Block-level Analysis: Granular complexity computation for each code block
• AST-Based Parsing: Uses Babel parser for accurate TypeScript/JavaScript/JSX code parsing
• No Pattern Matching: Pure algorithmic analysis without relying on pre-known patterns
• Conservative Estimates: Provides reasonable defaults for unknown code
• Built-in Method Knowledge: Knows complexity of basic Array/Object methods

Live Demo

Check the Monaco Editor integration demo: View Repo | Launch Demo

Quick Start

Installation

# npm
npm install @babel/parser worstcase

In a TypeScript project, add @babel/types

npm install @babel/types

Basic Usage

import { analyzeComplexity } from "worstcase";

// Example: Analyzing a bubble sort implementation
const code = `
function bubbleSort(arr) {
    for (let i = 0; i < arr.length; i++) {
        for (let j = 0; j < arr.length - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                [arr[j], arr[j + 1]] = [arr[j + 1], arr[j]];
            }
        }
    }
    return arr;
}
`;

const analysis = analyzeComplexity(code);
console.log(analysis.overall.time); // O(n^2)
console.log(analysis.overall.space); // O(1)

API Reference

analyzeComplexity(code: string, options?: Partial<WCOptions>): WCAnalysis

Analyzes JavaScript/TypeScript code and returns complexity information.

Parameters

Parameter	Type	Description
code	string	JavaScript/TypeScript source code to analyze
options	Partial<WCOptions> | undefined	Configure the analyzer

Returns: WCAnalysis

type WCOptions = {
    clean: boolean; // Whether or not to drop coefficients - default: true
};

interface WCAnalysis {
    overall: {
        time: string; // Overall time complexity (e.g., "O(n^2)")
        space: string; // Overall space complexity (e.g., "O(1)")
    };
    results: Array<{
        type: string; // AST node type
        node: Node; // Babel AST node: from @babel/types
        location: string; // Code location
        time: string; // Time complexity
        space: string; // Space complexity
    }>;
}

Example Response

{
    overall: {
        time: "O(n^2)",
        space: "O(1)"
    },
    results: [
        {
            type: "FunctionDeclaration",
            location: "Line 2",
            time: "O(n^2)",
            space: "O(1)",
            node: {...}
        }
        // ... more results
    ]
}

Limitations

This tool provides approximations, not perfect mathematical analysis. Current limitations:

• Dynamic behavior: Cannot analyze runtime-dependent complexity
• External dependencies: Unknown functions assumed to be O(1)
• Complex algorithms: May not recognize advanced algorithmic patterns
• Halting problem: Cannot guarantee termination analysis

Architecture

The analyzer uses a multi-step approach:

1. Parsing: Uses Babel parser to generate Abstract Syntax Tree (AST)
2. Traversal: Visits each AST node with specific complexity rules
3. Combination: Applies mathematical rules for combining complexities
4. Simplification: Reduces to dominant terms in Big O notation

Use Cases

worstcase is perfect for:

• Helping developers understand the performance implications of their code
• Catching potential performance bottlenecks during development
• Serving as an educational tool for learning complexity analysis
• Giving instant feedback without requiring manual calculation
• Giving real-time complexity hints via IDE integration

Contributing

Thank you for checking out this awesome project. Contributions are welcome!

Areas for improvement:

• Recursive pattern recognition: Advanced recurrence relation solving

Development Setup

1. Install Node.js (>=22) and pnpm (>=10)
2. Clone this repository

   git clone https://github.com/henryhale/worstcase.git
   cd worstcase

3. Install dependencies

   pnpm install

4. Run development server

   pnpm dev

5. Run tests

   pnpm test

6. Build for production

   pnpm build

Support

If you find this project useful, please consider giving it a star ⭐️ on GitHub!

License

Copyright (c) 2025-present Henry Hale.

MIT License - see LICENSE.txt file for details.