Property ‘value’ does not exist on type EventTarget in TypeScript [duplicate]

event.target here is an HTMLElement which is the parent of all HTML elements, but isn’t guaranteed to have the property value. TypeScript detects this and throws the error. Cast event.target to the appropriate HTML element to ensure it is HTMLInputElement which does have a value property:

(event.target as HTMLInputElement).value

Per the documentation:

Type the $event

The example above casts the $event as an any type. That simplifies the code at a cost. There is no type information that could reveal properties of the event object and prevent silly mistakes.

[…]

The $event is now a specific KeyboardEvent. Not all elements have a value property so it casts target to an input element.

(Emphasis mine)