You can use like this:

All values of object should have instance of String:

foo: PropTypes.objectOf(PropTypes.string), 

For further interest:

Any values of object can be passed:

foo: PropTypes.objectOf(PropTypes.any), 

Object can only have a and b as its property:

foo: PropTypes.shape({ a: PropTypes.string, b: PropTypes.number }), 

Or, custom validation:

foo: function(props, propName, componentName) { if (!/matchme/.test(props[propName])) { return new Error( 'Invalid prop `' + propName + '` supplied to' + ' `' + componentName + '`. Validation failed.' ); } }, 

To define your shape with PropTypes you would use something like:

import PropTypes from 'prop-types'; // your component const Component = () => <p>Hello world</p> Component.propTypes = { foo: PropTypes.shape({ a: PropTypes.string, b: PropTypes.string, }), } 

Apart from that I'm not sure what you mean :)

It really depends on whether you would like your object to be strongly typed or not. JS can be incredibly free with object types or you can use something like typescript to make everything strongly typed.

Im not entirely sure what you mean by a custom type checker, but if say this is being populated by a something external and you always want the variables in the object to be of type int, then you could add some logic to do so.

If you are more precise with the whole problem maybe I can help you futher