componentDidMount()
. This method is called after a component is mounted to the DOM. Any calls to setState()
here will trigger a re-rendering of your component. When you call an API in this method, and set your state with the data that the API returns, it will automatically trigger an update once you receive the data.
componentDidMount()
. It sets state after 2.5 seconds to simulate calling a server to retrieve data. This example requests the current total active users for a site. In the render method, render the value of activeUsers
in the h1
. Watch what happens in the preview, and feel free to change the timeout to see the different effects.
MyComponent
should render a div
element which wraps an h1
tag.
testString: assert((() => { const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); return (mockedComponent.find('div').length === 1 && mockedComponent.find('h1').length === 1); })(), 'MyComponent
should render a div
element which wraps an h1
tag.');
- text: Component state should be updated with a timeout function in componentDidMount
.
testString: assert((() => { const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); return new RegExp('setTimeout(.|\n)+setState(.|\n)+activeUsers').test(String(mockedComponent.instance().componentDidMount)); })(), 'Component state should be updated with a timeout function in componentDidMount
.');
- text: The h1
tag should render the activeUsers
value from MyComponent
's state.
testString: 'async () => { const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); const first = () => { mockedComponent.setState({ activeUsers: 1237 }); return mockedComponent.find(''h1'').text(); }; const second = () => { mockedComponent.setState({ activeUsers: 1000 }); return mockedComponent.find(''h1'').text(); }; assert(new RegExp(''1237'').test(first()) && new RegExp(''1000'').test(second()), ''The h1
tag should render the activeUsers
value from MyComponent
's state.''); }; '
```