What is tslint?

TSLint was a static analysis tool for TypeScript, the typed variant of JavaScript. A linter like TSLint reads your source code without running it and flags problems: style inconsistencies, potential bugs, code that is hard to maintain, and patterns that do not follow the rules your team has agreed on. It was created by Palantir and became widely adopted across the TypeScript community. An important note at the top of the README: TSLint is deprecated. Development stopped, and the community has moved to typescript-eslint, which is a set of TypeScript-specific rules that run inside ESLint. If you are starting a new TypeScript project today, you would use typescript-eslint rather than TSLint. Existing projects using TSLint are encouraged to migrate. When it was active, TSLint supported a large set of built-in rules covering readability and functionality checks, the ability to write custom rules, multiple output formats for reporting violations, and comment flags to disable specific rules on individual lines of code. It could automatically fix certain style violations. It integrated with most editors and build tools of the era, including VS Code, WebStorm, Vim, Emacs, Sublime Text, Eclipse, Atom, Grunt, Gulp, and MSBuild. The configuration system used a JSON file where you could extend shared presets (such as tslint:latest or tslint-react) and add or override rules. A sandbox environment called TSLint Playground was available for testing rules interactively without setting up a project. Third-party rule packages extended TSLint's built-in rules. Community contributions covered areas like Angular, React, RxJS, immutability enforcement, and rules inspired by the Clean Code programming philosophy.