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You think ESLint checks semicolons. It does more. It acts as a quality gate for your code.
ESLint does not read code as text. It uses a parser to turn code into an Abstract Syntax Tree. This is called an AST. The AST ignores spacing and comments. It only cares about meaning.
Every rule is a visitor. The visitor walks through the AST. It looks for specific patterns. If it finds a bad pattern, it reports an error.
This system solves three main problems:
- Logic bugs: It finds functions with no calls.
- Dead code: It finds imports you do not use.
- Security: It finds dangerous patterns.
Running a linter in your editor is helpful. Blocking merges in CI is better. It turns advice into policy. The code must be correct to merge.
Many teams want AI agents for quality. Boring tools often win. A linter is:
- Faster
- Cheaper
- Consistent
- Accurate
AI hallucinations are a risk. Static analysis does not guess.
The best teams automate their knowledge. They turn every bug into a rule. This builds memory for the whole team.