Typescript - Getting object values with keys - Element implicitly has an 'any' type because expression of type 'string' can't be used to index type

Question

I have an interface for a form values:

export interface FormProps {
  name: string
  customerIds: number[]
  primaryColor: string
  headingColor: string
  websiteLink?: string
  websiteLinkEnabled: boolean
  contactLink?: string
  contactLinkEnabled: boolean
  instagramLink?: string
  instagramLinkEnabled: boolean
  facebookLink?: string
  facebookLinkEnabled: boolean
  logo: File[]
  numberOfImages: number
}

I would like to check if the fields are dirty, by a function that takes an array of string that maps to each field and then check if there is a difference between the old and new values:

const colorsFields = ['primaryColor', 'headingColor']
checkIfFieldsAreDirty(colorsFields, initialValues, values)

const checkIfFieldsAreDirty = (fields: string[], initialValues: FormProps, values: FormProps): boolean => fields.some(field => initialValues[field] !== values[field]

But, I get a Typescript error:

Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'FormProps'.   No index signature with a parameter of type 'string' was found on type 'FormProps'.

How can I fix this?

Nullndr · Accepted Answer · 2022-12-02 10:23:38Z

1

You are using an array of string in order to access elements inside initialValues, in order to do this, you have to pass an array of keyof FormProps:

const colorsFields: (keyof FormProps)[] = ['primaryColor', 'headingColor']

An example here

answered Dec 2, 2022 at 10:23

Nullndr

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