flow type linting rules for ESLint

 Flow uses type inference to find bugs even without type annotations.
 It precisely tracks the types of variables as they flow through your program.
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 Flow is designed for JavaScript programmers.
 It understands common JavaScript idioms and very dynamic code.
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 Flow incrementally rechecks your changes as you work, preserving the
 fast feedback cycle of developing plain JavaScript.
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 Node.js is an event-based server-side JavaScript engine.