Integration with TypeScript / Mocha / other build processes

Are there any tutorials or documentation on integrating Expo with a different RN build process? For example, if we have an existing setup with TypeScript or want to use Mocha instead of Jest or whatever.


Hi! Have you gotten any further here? I’m myself specially interested in the Typescript part.

Hi again, I think I have a solution. Not sure it’s 100% or if it’s even a great approach. But I got it working :slight_smile: with gulp.

First install typescript via npm install (you probably already have).

Also install gulp and gulp-typescript via npm

npm i gulp gulp-typescript --save-dev

Also install various typings for react and react-native

npm i @types/react @types/react-native --save-dev

Now run

tsc --init

to create a tsconfig.json file.
Edit it to look like this:

    "compilerOptions": {
        "target": "es6",
        "jsx": "react",
        "noImplicitAny": true,
        "experimentalDecorators": true,
        "preserveConstEnums": true,
        "outDir": "build",
        "rootDir": "src",
        "sourceMap": true,
        "typeRoots": [
    "filesGlob": [
    "exclude": [
    "compileOnSave": false

Now create a gulpfile.js and paste the following:

var gulp = require('gulp');
var ts = require('gulp-typescript');

// Grab settings from tsconfig.json
var tsProject = ts.createProject('tsconfig.json');

gulp.task('build', function() {
    var tsResult = tsProject.src().pipe(tsProject());
    return tsResult.js.pipe(gulp.dest('build'));

gulp.task('watch', ['build'], function() {'src/**/*.ts', ['build']);'src/**/*.tsx', ['build']);

gulp.task('default', ['build']);

Now run:

gulp watch

You can now add tsx-files in the src directory. Let’s say I add CustomComponent.tsx:

import * as React from "react";
import { View } from "react-native";

export default class CustomComponent extends React.Component<any, any> {
    render() {
        return (
            <View />

I can then from main.js add:

import CustomComponent from "./build/CustomComponent ";

I might be missing some information here. But basically that’s it.
As I said, I dont know if this is a great approach. E.g. how do I make sure that things in the src directory isn’t included in the bundle?

I think the packager is smart enough that it will only build the bundle from the files that are used (following imports and requires from the entry point) so I think this approach should be clean.

A possibly more elegant one but that would take more work would be to tweak the packager to use the typescript transformer instead of babel.

I would also like to know how I would build this project using Typescript, similar to how create-react-app-typescript works. There doesn’t seem to be any examples, but a guideline on how this would be approached would be greatly appreciated.

Ideally we wouldn’t have to introduce a grunt/gulp workflow, and just tweak some configs.

EDIT: This appears to be quite helpfui: How to pass custom transformer to react-native-scripts

I’m coding in TypeScript using react-native-typescript-transformer. I’ve create a very simple demo app here: The type definitions for TypeScript still require a lot of work, though.

This helped me quite a lot:

IMO, TypeScript has been a lot better than Flow - I’m using both on two different projects

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