With my current knowledge, I am not able to understand what the Replace type is.

I did read the typescript documentation and learned part of what's happening in that line but it still was not enough for me to understand that.

CodePudding user response：

The type Replace is replacing properties in T, with properties in R.

To break it down:

1. Omit<T, keyof R> removes properties from T those with same name as properties in R.
2. Then & R intersects the resulting type from (1) with R. That means it adds the properties in R to the resulting type.

This may seem weird in that it re-adds the same properties to the resulting type those it removed earlier. But I suspect this was done to replace the type of the properties. Here is an example.

type Replace<T, R> = Omit<T, keyof R> & R;

type A = {
  prop1: string,
  prop2: string,
  prop3: string,
  prop4: string
};

type B = {
  prop3: number,
  prop4: number
};


type X = Replace<A, B>;

const x: X = {
  prop1: '1',
  prop2: '2',
  prop3: 3,
  prop4: 4
}

CodePudding user response：

It remove the common key of T and R from T, then intersect the result with R

as you can see, the common key is b, b of A is string, now it is boolean(from b of C)

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