# react-track Avoid it if you can, but for a certain class of (mostly animation-related) problems, you need to query the DOM. This library provides a way to track DOM elements in a functional, declarative manner. npm install react-track --save **Note: tweening, animation, and timeline-related stuff lives here: [`react-imation`](https://github.com/gilbox/react-imation)** - [Demo](http://gilbox.github.io/react-track/examples/demo/demo.html): [[source](https://github.com/gilbox/react-track/blob/master/examples/demo/app.js)] tracking components and tweening ## `` Used to track: - `document.documentElement` - `document.documentElement.getBoundingClientRect()` ``` import {TrackDocument, Track} from 'react-track'; import {getDocumentRect, getDocumentElement} from 'react-track/tracking-formulas'; // ...render: {rect =>

The height of documentElement is {rect.height}

} ``` ## `` Use `` to track any Component instance. For example, track an `

`: import {TrackDocument, Track} from 'react-track'; import {topTop} from 'react-track/tracking-formulas'; // ...render: {topTop => {(H2,posTopTop) =>
My top is {posTopTop}px from the viewport's top.
} } or track your `AwesomeComponent` // ...render: {topTop => {(AwesomeComponentTracked,posTopTop) => My top is {posTopTop}px from the viewport's top. } } It's important to note that `AwesomeComponent` must be stateful in this example. At the time of writing `react-track` does not support stateless functional components (SFCs) due to its reliance on the ref attribute, which such components do not provide. In order to track an SFC, wrap it in a [TrackedDiv](#trackeddiv-). Note that in the code above, there are two different scopes with a `topTop` variable. One scope is nested inside of the other. The `topTop` variable of the inner scope is the result of calling the `topTop` of the outer scope which returns type function. Here is the definition of the `topTop` function of the outer scope: export const topTop = containerRect => rect => (rect.top - containerRect.top); In the outer scope, the `` component supplies the `containerRect` argument, which comes from `document.documentElement.getClientBoundingRect()`. In the inner scope, the `` component supplies the `rect` argument which comes from `awesomeDOMElement.getClientBoundingRect()`. ### `trackedRef` `` supports an optional `trackedRef` prop which is type `Function`, and works the same way as the functional form of React's built-in `ref` prop. ## `` It's pretty common to need to track a div, so there's `TrackedDiv` component which is a slightly simpler version of `Track`: import {TrackDocument, TrackedDiv} from 'react-track'; import {topBottom} from 'react-track/tracking-formulas'; // ...render: {topBottom => {(posTopBottom) => My top is {posTopBottom}px from the viewport's bottom } } ## `tracking-formulas.js` The tracking components explained above all accept a `formulas` prop which expects an array of formula functions. When a tracking component renders, it passes the same arguments to all of the `formulas` and the results are passed as arguments into the function which you should supply to the `children` prop of the tracking component. The signature for all formula functions which are passed as an array into the `formulas` prop is: trackingFormula(rect, element) { // return any type } Of course, it's common to only utilize the first or second argument. Notice that all of the following are valid formulas that only utilize a single argument: const getDocumentRect = documentRect => documentRect; const getDocumentElement = (_,documentElement) => documentElement; const calculateScrollY = ({top}) => -top; Here's a valid formula which returns a valid formula: const centerCenter = (containerRect, container) => rect => (rect.top + rect.height / 2 - containerRect.top - container.clientHeight / 2); When a formula returns a formula, we are calculating something that relies on tracking two different elements. In this case, `centerCenter` calculates the distance from the vertical center of some element to the vertical center of some container element. The container element could be `document.documentElement` if you utilize `TrackDocument`, or it could be any other DOM element if you utilize `Track` or `TrackedDiv`. Creating custom formulas is relatively easy. Check out [`tracking-formulas.js`](https://github.com/gilbox/react-track/blob/master/src/tracking-formulas.js) for inspiration. ## Contributing ### Publishing to NPM - First make sure to bump the version number in `package.json` in accordance with semantic versioning practices. If you think a major version bump is warranted, go for it! # preparation npm run build-npm # actually publish to npm npm run publish - Create a git tag and publish it git tag vVERSION.NUMBER.WHATEVER git push origin vVERSION.NUMBER.WHATEVER

	Stars	Issues	Version	Updated	Created
react-animate-on-scroll			2.1.9	6 days ago	7 years ago
react-animations			1.0.0	7 years ago	8 years ago
react-track	339	2	0.4.4	7 years ago	9 years ago
react-transition-group	10,074	228	4.4.5	2 years ago	7 years ago

react-animate-on-scroll vs react-animations vs react-track vs react-transition-group

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