TypeScript transformer to remove .js from import and export statements

webpack.config.js

// https://github.com/Microsoft/TypeScript/issues/16577#issuecomment-343699395

const path = require('path');
const ts = require('typescript');
const { isImportDeclaration, isExportDeclaration, isStringLiteral } = require('tsutils/typeguard/node');

function getCustomTransformers() {
    return { before: [stripJsExt] }

    function stripJsExt(context) {
        return sourceFile => visitNode(sourceFile);

        function visitNode(node) {
            if ((isImportDeclaration(node) || isExportDeclaration(node)) &&
                node.moduleSpecifier && isStringLiteral(node.moduleSpecifier)) {
                const targetModule = node.moduleSpecifier.text;
                if (targetModule.endsWith('.js')) {
                    const newTarget = targetModule.slice(0, targetModule.length - 3);
                    return isImportDeclaration(node) ?
                        ts.updateImportDeclaration(
                            node,
                            node.decorators,
                            node.modifiers,
                            node.importClause,
                            ts.createLiteral(newTarget)
                        ) :
                        ts.updateExportDeclaration(
                            node,
                            node.decorators,
                            node.modifiers,
                            node.exportClause,
                            ts.createLiteral(newTarget)
                        );
                }
            }
            return ts.visitEachChild(node, visitNode, context);
        }
    }
}

module.exports = {
    entry: './src/index.ts',
    output: {
        path: path.resolve(__dirname, 'dist'),
        filename: 'app.bundle.js'
    },
    resolve: {
        extensions: ['.ts', '.tsx', '.js', '.json']
    },
    module: {
        rules: [
            { test: /\.tsx?$/, loader: 'ts-loader', options: { getCustomTransformers } }
        ]
    }
};

@AviVahl understood. Thanks again for the useful advices!