Use typescript to create object from array of objects-CodePudding

I have the following typescript code:

const a = [{ foo: 1 }, { bar: '2' }]

I wish to use a to create an object of the form:

const b = {
  foo: 1,
  bar: '2'
}

and the typing of b should be equivalent to the type:

type EquivalentType = {
  foo: number
  bar: string
}

Is this possible without casting? How can this be done?

CodePudding user response：

if you want this to be dynamic meaning you don't know what properties will be in the array you can do something like this:

const a = [{ foo: 1 }, { bar: '2' }]

let b = {};
for (let obj of a) {
  for (let property in obj) {
    b[property] = obj[property];
  }
}

console.log(b)

CodePudding user response：

// You might be able to simplify this
type TypeFromLiteral<T> = T extends string ? string : T extends number ? number : T extends boolean ? boolean : never;

// The "as const" part is important so that we can process the types
const a = [{ foo: 1 }, { bar: '2' }] as const;

// Get the final type
type ObjectUnion = typeof a[number];
type NewType = { [T in ObjectUnion as keyof T]: TypeFromLiteral<T[keyof T]> };

// By itself, this will get the correct value. However, we need to process the type separately and cast it to get what you want.
const b = Object.assign({}, ...a) as NewType;