[Solved]-Flow gives an error "Cannot assign [value] to this.[property] because property [property] is missing in [class]"-Reactjs

Use SyntheticInputEvent<*>

  handleClick = (e: SyntheticInputEvent<*>) => {
    this.targetElement = e.target.value;
  };

or

  handleClick = (e: SyntheticEvent<HTMLInputElement>) => {
    this.targetElement = e.target.value;
  };

You might want to check the docs and also cheet sheets