The code complexity analyzer scores your JavaScript or TypeScript code across 6 quality dimensions — cyclomatic complexity, nesting depth, function length, function count, comment density, and line length. Paste your code and get a maintainability report with specific recommendations.
Overall Score
Quality Dimensions
How we score
Cyclomatic Complexity (25%): Counts branching keywords (if, else, for, while, switch, case, &&, ||). Under 10 per file = excellent.
Nesting Depth (20%): Tracks the deepest level of brace nesting. 3 levels = good, 5+ = concerning.
Function Length (20%): Average lines per function. Under 20 lines = clean, over 40 = needs splitting.
Function Count (15%): Total functions in the file. Over 20 functions = consider splitting into modules.
Comment Density (10%): Ratio of comment lines to code lines. 10-25% is the sweet spot.
Line Length (10%): Percentage of lines exceeding 80 characters. Under 10% = clean.
How to Use the Code Complexity Analyzer
Code complexity is the silent killer of maintainability. A function that works perfectly today becomes a debugging nightmare six months later when requirements change. The code complexity analyzer gives you an objective score across the key dimensions that predict how painful your codebase will be to maintain.
Step 1: Paste your code
Copy any JavaScript or TypeScript file — a utility module, a React component, a Node.js controller. Paste the entire file into the textarea. The analyzer works best on individual files of 50-500 lines rather than entire concatenated bundles.
Step 2: Read the dimension breakdown
Each dimension gets a PASS, WARN, or FAIL rating with a specific recommendation. A FAIL on cyclomatic complexity means you have too many branching paths — extract conditions into named functions with clear intent. A FAIL on nesting depth often means nested if/else chains that can be flattened with guard clauses (early returns).
Step 3: Act on the recommendations
The most impactful improvements: (1) Break functions over 40 lines into smaller focused functions. (2) Replace deep nesting with early returns — instead of if (valid) { ... } wrapping 30 lines, use if (!valid) return; at the top. (3) Reduce cyclomatic complexity by extracting complex conditions into well-named boolean variables. (4) Add comments explaining the "why" not the "what" until comment density reaches 10-20%.
What score should you aim for?
A score of 80+ means your code is clean and maintainable. 60-79 is acceptable for production code with active development. Below 60 is a signal to prioritize refactoring before adding new features — the compound interest of technical debt starts to hurt around this threshold. Run the analyzer on each function individually if you need to pinpoint the worst offenders.
FAQ
What is cyclomatic complexity?
Cyclomatic complexity measures the number of independent paths through your code. It counts branches like if/else, for, while, switch/case, &&, and || operators. A complexity of 1-10 is simple and easy to test; 11-20 is moderate; above 20 is complex and risky. High complexity means more possible execution paths and more test cases needed.
What is a good code complexity score?
A score of 80-100 means your code is clean and maintainable. 60-79 is moderate — some functions could be refactored. Below 60 indicates high complexity that makes code harder to understand, test, and debug. The score combines cyclomatic complexity, nesting depth, function length, and comment density.
How deep should nesting go in code?
Most style guides recommend no more than 3-4 levels of nesting. Deep nesting (5+ levels) is a code smell that makes logic hard to follow and test. Refactoring techniques include early returns, extracting helper functions, or using guard clauses to flatten nested if/else chains.
How long should a function be?
Functions under 20 lines are easy to understand at a glance. 20-40 lines is acceptable but consider splitting. Over 40 lines often means a function is doing too much and should be refactored into smaller, single-purpose functions. The single responsibility principle is the guiding rule.
Is this tool free and private?
Yes, completely free. Your code never leaves your browser — all analysis runs locally in JavaScript. No code is sent to any server.
Does this tool work with TypeScript?
Yes. The analyzer uses regex-based pattern matching that works with JavaScript, TypeScript, and similar syntax. It detects function declarations, arrow functions, control flow keywords, and nesting patterns common to both languages.