ab-test-jsx

React (JS) based client for consuming AB test logic in your app.

yarn add ab-test-jsx

# or with npm

npm install ab-test-jsx --save

Setup

👉 ab-test-jsx is a consumer library for AB tests, provide results of allocation to running tests on the client. It's advised to allocate on the server-side and simply hydrate the application with allocation state on first render.

ab-test-jsx uses the ContextAPI to provide allocation information to components via Components/Hook/HOC. Set-up the ContextAPI provider before consuming the AB test allocation results in child components. Either use ABTestsProvider or the higher order component - withABTestsProvider

<ABTestsProvider /> component

The app should be wrapped at the root level. Pass the ab tests allocation results object using the abTests prop:

<ABTestsProvider abTests={abTests}>
  <AppRoot {...props} />
</ABTestsProvider>

Additional settings can be passed:

defaultVariant: 'A' // what variant should be returned if experiment cannot be found in the context. Defaults to A

withABTestsProvider Higher Order Component

Wrap export of application root with the HOC and pass the ab tests allocation results object using param:

const WrappedApp = withABTestsProvider(App, abTests)

It's also possible to use a function that will return abTests - to access data from props when decorating the component:

const abTestsSelector = props => props.tests
const WrappedApp = withABTestsProvider(App, abTestsSelector)

ABTests context

AB tests or allocation results should be an object (dictionary) that specifies the name of the test (key) and allocated variant of that test for the session: A or B:

type Variant = 'A' | 'B'

interface ABTests {
  [key: string]: Variant
}

Usage

There are multiple ways of accessing AB tests allocation results in components. Either compose the JSX tree with ABTest component, use useABTests hook to access some getter functions, or experiment with conditional rendering of 2 components as single one based on allocation result - withABTest. For custom logic, always decorate components props with the abTests context by using withABTests HOC.

<ABTest /> component

<ABTest /> component is simple conditional renderer - it takes 2 props: name and variant and based on that information, will render its children. It can be used to compose complex layouts based on AB test:

<ABTest name="changeHeaderSize" variant="A">
  <h1>Welcome on our page!</h1>
</ABTest>
<ABTest name="changeHeaderSize" variant="B">
  <h2>Welcome on our page!</h2>
</ABTest>

In above example, if user gets A variant of the test changeHeaderSize, they will get layout based on h1 heading size. For B variant, user gets h2 as heading.

💡 Note that when composing AB tests, don't keep A & B variants of ` next to each other, as well you are not limited to single usage. It's possible to wrap as many children as needed as long as they are in same tree as Context Provider

API

prop	type	required	defaultValue	Description
name	string \| number	true	-	key value used to look up AB test allocation
variant	A \| B	true	-	specifies under what allocation the children of the component will get rendered
children	React.Node[]	true	-	conditionally rendered components

---

useABTests() hook

Use the useABTests() React hook to access the AB tests related values in functional components. Hook will return an object with 3 functions that can be called to evaluate allocation:

const Header: React.FC = () => {
  const { getVariant, isB, isA } = useABTests()

  const isNewHeader = isB('changeHeaderSize') // We can test and write conditional logic based on allocation

  return isNewHeader ? <h1>Super dope header</h1> : <span>Super dope header</span>
}

Use a function that is needed for each use case - example above lists them all. Since this is simple object destructuring use isB() from the hook:

const { isB } = useABTests()

API

getVariant(name: string | number) => Variant - use this function to get current variant of AB test. name is the name of the test, returns Variant type (A | B | Z)

isB(name: string | number) => boolean - use this function to check if specific AB tests is allocated to B variant. name is the name of the test, returns boolean

isA(name: string | number) => boolean - use this function to check if specific AB tests is allocated to A variant. name is the name of the test, returns boolean

---

withABTest Higher Order Component

USE if there are 2 different components that are suposed to be 2 different variants of AB tests. Lets say you implemented new complex Header layout and you want to render it only for B variant users:

const HeaderUnderABTest = withABTest(Header, NewHeader, 'useNewHeader')

In above example, Header is A variant component, NewHeader is our B variant component, and 3rd parameter is the test name. Props of both A and B variants are both merged together so it's easier to use the tested component in code:

<HeaderUnderABTest somePropFromHeader={1} anotherPropButFromNewHeader={2} />

API

param	type	description
AVariantComponent	React.ComponentType	A variant of component
BVariantComponent	React.ComponentType	B variant of component
abTestName	string \| number	key value used to look up AB test allocation

Returns a component that will conditionally render either A or B variant parameter component based on test name and allocation. Props of both A and B variants are merged together and exposed.

withABTests Higher Order Component

If you need to pass all experiments from context as props into a component, use withABTests Higher Order Component. It will decorate the component with abTests prop containing all allocation data:

const SomeComponent = ({ text, abTests }) => (
  <>
    <span>{text}</span>
    {abTests.test1 === 'A' && <span>test1=A</span>}
    {abTests.test1 === 'B' && <span>test1=B</span>}
  </>
)

const SomeComponentWithABTests = withABTests(SomeComponent)

Typescript support

The library supports fully typed experience for allocation data as well as all components. To ensure type safety with AB tests names provide a type defining schema as a generic argument:

import * as ABTestJsx from 'ab-test-jsx'

type TestsSchema = {
  test1: ABTestJsx.Variant
  test2: ABTestJsx.Variant
}

const {
  ABTest,
  ABTestsProvider,
  useABTests,
  withABTest,
  withABTests,
  withABTestsProvider,
} = ABTestJsx as ABTestJsx.ABTestsModule<TestsSchema>

Use exports instead of going with library directly, and all AB tests names will become type checked against the declared schema!

Following example will result in type checking error, since test3 is not a property that exists on TestsSchema type:

<ABTest name="test3" variant="B">
  <span>test2=B</span>
</ABTest>