How TypeScript uses type inference

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Skillful use of type derivation

TypeScript can infer (check) the types of variables according to some simple rules.

For example, a simple add function

Function add (a: number, b: number) {return a + b}

TypeScript can derive the return value of the function from the operator of the parameter and return.

If you want to get the type of the function as a whole, you can use typeof

Pay attention to distinguish it from the typeof in JavaScript

Type AddFn = typeof add

Of course, the above situation is relatively simple. Sometimes our return value type is actually quite complex. At this time, we can easily get the return value type with the help of type derivation and ReturnType.

Type returnType = ReturnType / / number

The above techniques are very suitable for coding redux, so we can omit a lot of repetitive code. After all, the coding work of redux is very tedious.

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