freeCodeCamp/curriculum/challenges/english/03-front-end-libraries/react/use-default-props.english.md

id	title	challengeType	isRequired
5a24c314108439a4d403616b	Use Default Props	6	false

Description

React also has an option to set default props. You can assign default props to a component as a property on the component itself and React assigns the default prop if necessary. This allows you to specify what a prop value should be if no value is explicitly provided. For example, if you declare MyComponent.defaultProps = { location: 'San Francisco' }, you have defined a location prop that's set to the string San Francisco, unless you specify otherwise. React assigns default props if props are undefined, but if you pass null as the value for a prop, it will remain null.

Instructions

The code editor shows a ShoppingCart component. Define default props on this component which specify a prop items with a value of 0.

Tests

tests:
  - text: The <code>ShoppingCart</code> component should render.
    testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ShoppingCart)); return mockedComponent.find('ShoppingCart').length === 1; })(), 'The <code>ShoppingCart</code> component should render.');
  - text: 'The <code>ShoppingCart</code> component should have a default prop of <code>{ items: 0 }</code>.'
    testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ShoppingCart)); mockedComponent.setProps({items: undefined}); return mockedComponent.find(''ShoppingCart'').props().items === 0; })(), ''The <code>ShoppingCart</code> component should have a default prop of <code>{ items: 0 }</code>.'');'

Challenge Seed

const ShoppingCart = (props) => {
  return (
    <div>
      <h1>Shopping Cart Component</h1>
    </div>
  )
};
// change code below this line

After Test

ReactDOM.render(<ShoppingCart />, document.getElementById('root'))

Solution

const ShoppingCart = (props) => {
  return (
    <div>
      <h1>Shopping Cart Component</h1>
    </div>
  )
};

// change code below this line
ShoppingCart.defaultProps = {
  items: 0
}