typescript 函数返回一个对象，该对象的键是输入对象的值

Posted 2021-05-20

/**
* Declare the type for the following fuction
* e.g. const mappingFunc = obj => ({[obj.name]: true})
**/

const mappingFunc = <T extends string>(arg: {name: T}): Record<T, boolean> => ({
  [arg.name]: true
})

const obj = {
  name: 'foo' as 'foo' // <-- narrow down the type from `string` to `"foo"` (String Literal Type)
}

const output = mappingFunc<typeof obj.name>(obj);
console.log(output.foo) // true
console.log(output.bar) // error:  TS2339: Property 'bar' does not exist on type 'Record<"foo", boolean>'.