TypeScript icon, indicating that this package has built-in type declarations

    1.0.0 • Public • Published



    yarn add react-native-viewport-helpers or npn install react-native-viewport-helpers


    Works like a regular useLayoutEffect hook.

    Takes in a reffrom useRef. An effect function that works just like useEffect meaning a cleanup can be returned. Dependencies for the effect, and a delay that is by default 500ms.

    This works through polling, so it's not the most performance friendly thing, but it works.

    import * as React from 'react';
    import { useIsInViewPortEffect } from 'react-native-viewport-helpers';
    import { useRef } from 'react';
    import { View, Text, ScrollView } from 'react-native';
    const App = () => {
      const arr = new Array(100).fill(1);
      return (
          {, i) => (
            <div key={`key${i}`}>{i}</div>
          <Component />
          {, i) => (
            <div key={`key${i}`}>{i}</div>
    const Component = () => {
      const ref = useRef < any > null;
        () => {
          console.log('Hello World');
          return () => {
      return (
        <View ref={ref}>


    This was made with TSDX + a few changes, readme for that below


    TSDX scaffolds your new library inside /src, and also sets up a Parcel-based playground for it inside /example.

    The recommended workflow is to run TSDX in one terminal:

    npm start # or yarn start

    This builds to /dist and runs the project in watch mode so any edits you save inside src causes a rebuild to /dist.

    Then run the example inside another:

    cd example
    npm i # or yarn to install dependencies
    npm start # or yarn start

    The default example imports and live reloads whatever is in /dist, so if you are seeing an out of date component, make sure TSDX is running in watch mode like we recommend above. No symlinking required, we use Parcel's aliasing.

    To do a one-off build, use npm run build or yarn build.

    To run tests, use npm test or yarn test.


    Code quality is set up for you with prettier, husky, and lint-staged. Adjust the respective fields in package.json accordingly.


    Jest tests are set up to run with npm test or yarn test. This runs the test watcher (Jest) in an interactive mode. By default, runs tests related to files changed since the last commit.

    Setup Files

    This is the folder structure we set up for you:

      index.tsx       # test your component here in a demo app
      index.tsx       # EDIT THIS
      blah.test.tsx   # EDIT THIS
    package.json         # EDIT THIS
    React Testing Library

    We do not set up react-testing-library for you yet, we welcome contributions and documentation on this.


    TSDX uses Rollup v1.x as a bundler and generates multiple rollup configs for various module formats and build settings. See Optimizations for details.


    tsconfig.json is set up to interpret dom and esnext types, as well as react for jsx. Adjust according to your needs.

    Continuous Integration


    to be completed


    to be completed


    Please see the main tsdx optimizations docs. In particular, know that you can take advantage of development-only optimizations:

    // ./types/index.d.ts
    declare var __DEV__: boolean;
    // inside your code...
    if (__DEV__) {

    You can also choose to install and use invariant and warning functions.

    Module Formats

    CJS, ESModules, and UMD module formats are supported.

    The appropriate paths are configured in package.json and dist/index.js accordingly. Please report if any issues are found.

    Using the Playground

    cd example
    npm i # or yarn to install dependencies
    npm start # or yarn start

    The default example imports and live reloads whatever is in /dist, so if you are seeing an out of date component, make sure TSDX is running in watch mode like we recommend above. No symlinking required!

    Deploying the Playground

    The Playground is just a simple Parcel app, you can deploy it anywhere you would normally deploy that. Here are some guidelines for manually deploying with the Netlify CLI (npm i -g netlify-cli):

    cd example # if not already in the example folder 
    npm run build # builds to dist 
    netlify deploy # deploy the dist folder 

    Alternatively, if you already have a git repo connected, you can set up continuous deployment with Netlify:

    netlify init
    # build command: cd example && yarn && yarn build 
    # directory to deploy: example/dist 
    # pick yes for netlify.toml 

    Named Exports

    Per Palmer Group guidelines, always use named exports. Code split inside your React app instead of your React library.

    Including Styles

    There are many ways to ship styles, including with CSS-in-JS. TSDX has no opinion on this, configure how you like.

    For vanilla CSS, you can include it at the root directory and add it to the files section in your package.json, so that it can be imported separately by your users and run through their bundler's loader.

    Publishing to NPM

    We recommend using

    Usage with Lerna

    When creating a new package with TSDX within a project set up with Lerna, you might encounter a Cannot resolve dependency error when trying to run the example project. To fix that you will need to make changes to the package.json file inside the example directory.

    The problem is that due to the nature of how dependencies are installed in Lerna projects, the aliases in the example project's package.json might not point to the right place, as those dependencies might have been installed in the root of your Lerna project.

    Change the alias to point to where those packages are actually installed. This depends on the directory structure of your Lerna project, so the actual path might be different from the diff below.

       "alias": {
    -    "react": "../node_modules/react",
    -    "react-dom": "../node_modules/react-dom"
    +    "react": "../../../node_modules/react",
    +    "react-dom": "../../../node_modules/react-dom"

    An alternative to fixing this problem would be to remove aliases altogether and define the dependencies referenced as aliases as dev dependencies instead. However, that might cause other problems.


    npm i react-native-viewport-helpers

    DownloadsWeekly Downloads






    Unpacked Size

    35.1 kB

    Total Files


    Last publish


    • rjerue