Typescript React empty function as defaultProps

user_3578693 0
Viewed 17701

I have a Stateless Functional Component with an optional function parameter as property (onClick), I tried to define an empty function as default property to be able to do safely in my component :

 <span onClick={props.onClick} />

But I have the following error : 'Expression expected.'

interface IProps {
  size?: sizeType;
  onClick?: (e:any) => void;
}
const Foo: React.SFC = (props: IProps) => {
  // ...
};
const defaultProps: IProps = {
   size: 'default',
   onClick: () => void <-- Expression expected.
};
Foo = defaultProps;

How can I should do this?

typescript2.0 typescript-typings typescript reactjs
4 Answers

You cannot use void in javascript as return value. Instead of void, use null as return value.

onClick: () => null
user_88991930

You can use the following:

const defaultProps: IProps = {
   size: 'default',
   onClick: () => void(0)
};
user_6068210

I think using lodashes noop might be a good option because depending on the number of re-renders the component will have BEFORE the component has access to the prop, it will create that many references to an anonymous function that essentially is a place holder for the function you need. Something like:

import noop from 'lodash/noop';
MyComponent.defaultProps = {
  myfunc: noop,
};

Its a small optimization but also prevents the developer from creating an anonymous function for every default prop declaration that a func is needed in.

user_68408850
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