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Pavel M
Pavel M

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TypeScript ValidityState

#help #typescript #beginners 
const input: HTMLElement = e.target
const validity: ValidityState = input.validity
setValidity(validity.valid)
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I'm just getting into typescript and having a problem with the ValidityState API: the second line gets a red squiggly underline with Unsafe assignment of an 'any' value.

What's the proper course of action here?

Top comments (3)

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harry0000 profile image
harry •

HTMLElement does not have readonly validity: ValidityState property. Only the following elements have that property.

github.com/microsoft/TypeScript/bl...

  • HTMLButtonElement
  • HTMLFieldSetElement
  • HTMLInputElement
  • HTMLObjectElement
  • HTMLOutputElement
  • HTMLSelectElement
  • HTMLTextAreaElement

If you are using React, you can write as follows:

TS playground link

const input: React.FC = () => {
    return (
        <input onChange={(e) => {
          const input: HTMLInputElement = e.target
          const validity: ValidityState = input.validity
          setValidity(validity.valid)
        }}/>
    )
}
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or

const input: React.FC = () => {
    return (
        <input onChange={(e) => {
          // e: React.ChangeEvent<HTMLInputElement>
          setValidity(e.target.validity.valid)
        }}/>
    )
}
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harry0000 profile image
harry •

Or if you wanted to define a handler function, you can write as follows:

const handler: (e: React.ChangeEvent<HTMLInputElement>) => void = (e) => {
    // ...
}
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or

const handler = (e: React.ChangeEvent<HTMLInputElement>): void => {
    // ...
}
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vkrms profile image
Pavel M •

Thanks a bunch! It helped a lot.

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