property 27value 27 does not exist on type 27htmlelement 27

1document.getElementById() returns the type HTMLElement which does not contain a value property.
2The subtype HTMLInputElement does however contain the value property.
3
4So a solution is to cast the result of getElementById() to HTMLInputElement like this:
5
6var inputValue = (<HTMLInputElement>document.getElementById(elementId)).value;
7<> is the casting operator in typescript.
8See TypeScript: casting HTMLElement: https://fireflysemantics.medium.com/casting-htmlelement-to-htmltextareaelement-in-typescript-f047cde4b4c3
9
10The resulting javascript from the line above looks like this:
11
12inputValue = (document.getElementById(elementId)).value;
13i.e. containing no type information.