Type Checking

ScandiPWA uses PropTypes to help verify that the expected props are passed, and catch bugs

PropTypes is a library for React that verifies at runtime if props have the correct type, and if required props are passed.

PropTypes are only used in development builds, which means that production builds will be more efficient - but it also means that you should not rely on PropTypes being present in the production build!

PropTypes are declared as a static field:

component/CategoryPaginationLink/CategoryPaginationLink.component.js (annotated excerpt)

import { ChildrenType } from 'Type/Common';

export class CategoryPaginationLink extends PureComponent {
    static propTypes = {
        // component children are treated as props in React
        // by leaving out .isRequired, we make them optional
        children: ChildrenType,
        // we expect the getPage prop to be a function
        // it is required, so this will emit a warning if
        // getPage is not provided
        getPage: PropTypes.func.isRequired,
        // isCurrent expects a boolean
        isCurrent: PropTypes.bool.isRequired,
        // expects a string
        url_path: PropTypes.string.isRequired,
        // expects a number
        pageNumber: PropTypes.number.isRequired
    };
    
    static defaultProps = {
        // we must provide a default value for every prop that
        // is optionalex
        children: []
    };

Advanced Types

Sometimes you want to specify that a prop expects something more complex than a number or a string. You can check the official documentation to learn how to use:

• instanceOf to expect an instance of a class

• oneOf to expect an enum-like value that can have one of the specified values

• oneOfType to indicate that this prop may have one of the specified types

• arrayOf or objectOf to specify that this prop is an array or object where each value has the specified type

• shape or exact to specify that the prop should be an object, as well as what keys and values you expect it to have

For example, you could specify that a prop expecting a payment method should be given an object with two string properties:

PropTypes.shape({
    code: PropTypes.string,
    title: PropTypes.string
});

However, it is likely that this "complex" type would be needed in multiple places in the application. Copy-pasting the same PropType definition would lead to code duplication, and a hard-to-maintain codebase. Instead, we prefer defining these types in the type directory and exporting them for re-use:

type/Checkout.js (excerpt)

import PropTypes from 'prop-types';

export const paymentMethodType = PropTypes.shape({
    code: PropTypes.string,
    title: PropTypes.string
});

Now, we can use this type definition anywhere we want:

component/CheckoutPayment/CheckoutPayment.component.js (excerpt)

import { paymentMethodType } from 'Type/Checkout';

/** @namespace Component/CheckoutPayment/Component */
export class CheckoutPayment extends PureComponent {
    static propTypes = {
        method: paymentMethodType.isRequired,
        onClick: PropTypes.func.isRequired,
        isSelected: PropTypes.bool
    };