How can I declare a PropType corresponding to a nullable number?

Question

I\'m looking for a PropType that means

\"this is required, and it will either be a number or be null\"

In other words,

Answer 1

import propTypes from 'prop-types';

const nullable = propType => (props, propName, ...rest) =>
  props[propName] === null ? null : propType(props, propName, ...rest);

const testMe = {
  a: 'string',
  b: 420,
  c: null,
  d: undefined,
  e: undefined
};

const testSchema = {
  a: nullable(propTypes.string.isRequired),
  b: nullable(propTypes.string.isRequired),
  c: nullable(propTypes.number.isRequired),
  d: nullable(propTypes.bool.isRequired),
  e: nullable(propTypes.number)
};

propTypes.checkPropTypes(testSchema, testMe, 'prop', 'testMe');
// Warning: Failed prop type: Invalid prop `b` of type `number` supplied to `testMe`, expected `string`.
// Warning: Failed prop type: The prop `d` is marked as required in `testMe`, but its value is `undefined`.