Codacy - Automatically reviews code style, security, duplication, complexity, and coverage on every change while tracking code quality throughout your sprints.

DeepSource - Automated code reviews with static analysis.

PyLint - Pylint is a Python source code analyzer which looks for programming errors.

JavaScript Operator Lookup - A full list of JavaScript operators with examples

SonarQube - SonarQube, a core component of the Sonar solution, is an open source, self-managed tool that systematically helps developers and organizations deliver Clean Code.

JavaScripting - Ranking of top JavaScript libraries, frameworks, and plugins