I have input data in this form:

const input = {
    postcode: ['0000']
    submitted: ['yes']
}

const output = {
    postcode: '0000'
    submitted: 'yes'
}

How to create interface for input data?

I tried:

interface inputData {
    postcode: string[]
    submitted: string[]
}

interface outputData {
    postcode: string
    submitted: string
}

But I get error while applying it:

const extract = (input: inputData[]): outputData => {
  for (const key in input) {
    if (Object.hasOwnProperty.call(input, key)) {
      input[key] = input[key][0]; // Error here
    }
  }
  const output: any = input;
  return output;
}

Error: Element implicitly has an 'any' type because expression of type '0' can't be used to index type 'inputData'. Property '0' does not exist on type 'inputData'.

CodePudding user response：

Here is a working version

function hasOwnProperty<X extends {}, Y extends PropertyKey>
  (obj: X, prop: Y): obj is X & Record<Y, unknown> {
  return obj.hasOwnProperty(prop)
}

interface inputData {
    postcode: string[];
    submitted: string[];
}
type outputData = inputData;

const extract = (input: inputData): outputData => {
    for (const key in input) {
        if (hasOwnProperty(input, key)) {
            const value = input[key];

            if (value instanceof Array) {
                input[key] = value[0];
            }
        }
    }
    const output: any = input;
    return output;
}

CodePudding user response：

From the information you've provided the type of inputData is Record<string,string[]>` Record is a utility type (Link)

    postcode: ['0000'],
    submitted: ['yes']
}

type inputDataT = Record<string,string[]>

interface inputData {
    postcode: string[]
    submitted: string[]
}

const extract = (input: inputDataT) => {
  const output: any = input;
  for (const key in input) {
    if (Object.hasOwnProperty.call(input, key)) {
      output[key] = input[key][0];
    }
  }

  return output;
}
console.log(extract(inputData))

Also if you're sure that there will only ever be one string in the property value array you can make it stronger as follows:

type inputDataT = Record<string,[string]>
const inputData:inputDataT = {
    postcode: ['0000'],
    submitted: ['yes']
}

Playground

CodePudding user response：

You can define an interface with an indexer:

interface EnumServiceGetOrderBy {
    [index: number]: { id: number; label: string; key: any };
}