The property ‘value’ does not exist on value of type ‘HTMLElement’

Based on Tomasz Nurkiewiczs answer, the “problem” is that typescript is typesafe. 🙂 So the document.getElementById() returns the type HTMLElement which does not contain a value property. The subtype HTMLInputElement does however contain the value property.

So a solution is to cast the result of getElementById() to HTMLInputElement like this:

var inputValue = (<HTMLInputElement>document.getElementById(elementId)).value;

<> is the casting operator in typescript. See the question TypeScript: casting HTMLElement.

If you’re in a .tsx file the casting syntax above will throw an error. You’ll want to use this syntax instead:

(document.getElementById(elementId) as HTMLInputElement).value

The resulting javascript from the line above looks like this:

inputValue = (document.getElementById(elementId)).value;

i.e. containing no type information.