Lesson 02 · 9 min
Inference: when you don't need to write the type
The compiler already knows the type. An annotation is needed when it can't guess.
The most common beginner mistake is putting : string on every variable. TS infers the type from the value anyway. That's type inference: let count = 0 is already a number. Write annotations at the boundaries: function arguments, values returned by a public API, an empty initial state.
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