I have been searching for answer an all weekend. To no avail. I have been down the webpack rabbit hole with elixir 6 and back to browserify.

This gist here looked promising: https://gist.github.com/sagalbot/6150d4f536af7b4c4f9a9879856e595d

//  Default babel presets are ['es2015', 'react']
//  https://babeljs.io/docs/plugins/preset-stage-2/
elixir.config.js.babel.options.presets = ['es2015', 'stage-2'];

However elixir.config.js.babel is undefined — why is that? Was there a refactor done? I can't get it working.

All I want to do is enable stage-2. (https://babeljs.io/docs/plugins/preset-stage-2/)

My gulp file

require("laravel-elixir-remove");
require("laravel-elixir-bless");
require("laravel-elixir-browserify-official");
//require('laravel-elixir-scss-lint'); // this doesn't work under elixir ^6.0.0-10
require('elixir-typescript');
require("./gulp/ts.lint");

var elixir = require("laravel-elixir");
var jsonminify = require("jsonminify");
var config = require("./gulp/parse.config");
var argv = require("yargs").argv;
var fs = require("fs");
elixir.config.js.babel.enabled = true;
// grab the JSON file and make a copy of it.
// strip out the comments from the JSON file using jsonminify
var ORIGINAL_CONFIG = config.getJSON("./build.config.json");

//set the replacement section of the JSON file to modify the remainder of the JSON
config.setConfigKey("replacements");
config.parse(ORIGINAL_CONFIG);
elixir = config.setElixirPaths(elixir);

/*======================================================================================*/
// BROWSERIFY OPERATIONS
/*======================================================================================*/
var BROWSERIFYCONFIG = elixir.config.js.browserify;

BROWSERIFYCONFIG.plugins.push({
    name: "tsify", options: {
        target: "es5",
        experimentalDecorators: true,
        babelify: {
            extensions: [".tsx", ".ts"]
        }
    }
});

// can't get this working, I can't enable the spread/rest operator.
// elixir.config.js.browserify.transformers
//     .find(transformer => transformer.name === 'babelify')
//     .options.plugins = [
//     'syntax-object-rest-spread',
//     'transform-object-rest-spread'
// ];

BROWSERIFYCONFIG.plugins.push(
    {
        name: "factor-bundle",
        options: {
            // generate js files from the input, the order is crucial
            outputs: config.get("browserify.in", "js")
        }
    }
);

// this is undefined. When was the babel property removed from the elixir config object?!!
//console.log(elixir.config.js.babel);
//elixir.config.js.babel.options.presets = ['es2015', 'stage-2'];

/*======================================================================================*/
// BUILD
/*======================================================================================*/
elixir(build);
function build(mix) {

    if (!argv.hasOwnProperty("scss")) {
        // if there is no public dir, create it, as browserify expects
        if (!fs.existsSync(config.get("replacements.outPath"))) {
            fs.mkdirSync(config.get("replacements.outPath"));
            fs.mkdirSync(config.get("replacements.js"));
        }

        // browserify node_modules and write out
        mix.browserify(
            // factor all the files in order:
            config.get("browserify.in", "ts"),
            // and generate one file that is common to all of them:
            config.get("browserify.out", "js")
        );
    }
    //
    // if (!argv.hasOwnProperty("js")) {
    //
    //     // concatenate js files first
        mix.scripts(
            config.get("concat.in", "js"),
            config.get("concat.out", "js")
        );
    //
    //     //generate the css ( note we can't loop over )
    //     mix.sass(config.get('scss.0.in', 'scss'), config.get('scss.0.out', 'css'),{sourceComments:true})
    //         .sass(config.get('scss.1.in', 'scss'), config.get('scss.1.out', 'css'))
    //         .sass(config.get('scss.2.in', 'scss'), config.get('sass.2.out', 'css'))
    //         .sass(config.get('scss.3.in', 'scss'), config.get('scss.3.out', 'css'))
    //         .browserSync({
    //             files: ["**/*.css", "**/*.js", "**/*.php"],
    //             proxy: "website.mock",
    //             port: 4000,
    //             logPrefix: "Laravel Eixir BrowserSync"
    //         });
    //
    //     if(!argv.hasOwnProperty("production")){
    //         mix.scssLint(config.get('sasslint.in', 'scss'));
    //         mix.tslint(config.get("tslint.in", "ts"), config.getJSON(config.get("tslint.rules", "json")));
    //     }
    //
    //     // copy debug files over — temporary
    //     mix.copy(config.get('copy.0.in', 'css'), config.get('copy.0.out', 'css'))
    //         .copy(config.get('copy.1.in', 'css'), config.get('copy.1.out', 'css'))
    //         .copy(config.get('copy.2.in', 'js'), config.get('copy.2.out', 'js'))
    //         .copy(config.get('copy.3.in'), config.get('copy.3.out'))
    //         .bless(config.get('bless.0.in', 'css'), {imports: true});
    // }
}

I have a .babelrc file

{
  "presets": ["stage-2"],
  "comments": true
}

Which seems to be ignored.

Package.json

{
  "devDependencies": {
    "alterclass": "git+https://github.com/sidouglas/alter-class#1.0",
    "babel": "^6.5.2",
    "babel-core": "^6.10.4",
    "babel-preset-stage-2": "^6.13.0",
    "babel-register": "^6.9.0",
    "bootstrap-pull": "git+https://github.com/sidouglas/bootstrap-pull.git#3.0.2",
    "browserify-shim": "^3.8.12",
    "dot-object": "^1.4.1",
    "elixir-jasmine": "0.0.4",
    "gulp": "^3.9.1",
    "gulp-replace-task": "^0.11.0",
    "gulp-tslint": "^6.0.1",
    "jasmine-fixture": "^2.0.0",
    "jasmine-jquery": "^2.1.1",
    "jsonminify": "^0.4.1",
    "karma": "^1.1.1",
    "karma-chrome-launcher": "^1.0.1",
    "karma-firefox-launcher": "^1.0.0",
    "karma-ios-simulator-launcher": "0.0.4",
    "karma-jasmine": "^1.0.2",
    "karma-safari-launcher": "^1.0.0",
    "laravel-elixir": "^6.0.0-10",
    "laravel-elixir-bless": "^2.0.0",
    "laravel-elixir-browserify-official": "^0.1.3",
    "laravel-elixir-browsersync": "^0.1.5",
    "laravel-elixir-browsersync-official": "^1.0.0",
    "laravel-elixir-remove": "^0.2.1",
    "lodash": "^4.13.1",
    "node-sass": "^3.8.0",
    "retyped-bowser-tsd-ambient": "0.0.0-0",
    "run-sequence": "^1.2.1",
    "sass-convert": "^0.5.2",
    "supplant": "^0.2.0",
    "tsify": "^1.0.4",
    "tslint": "^3.13.0",
    "typescript": "^1.9.0-dev.20160605-1.0",
    "yargs": "^4.8.0"
  },
  "dependencies": {
    "babel-plugin-transform-object-rest-spread": "^6.8.0",
    "babel-preset-es2015": "^6.14.0",
    "babel-preset-react": "^6.11.1",
    "boilerplate": "^0.5.0",
    "bootstrap": "^3.3.6",
    "bootstrap-sass": "^3.3.6",
    "bootstrap-select": "^1.10.0",
    "bowser": "^1.4.2",
    "del": "^2.2.0",
    "elixir-typescript": "^2.0.0",
    "factor-bundle": "^2.5.0",
    "gulp-change": "^1.0.0",
    "gulp-shell": "^0.5.2",
    "include-media": "^1.4.5",
    "jquery": "^2.2.4",
    "jquery-replace-class": "0.0.1",
    "lodash": "^4.14.0",
    "material-kit": "git://github.com/tfsimondouglas/material-kit-bootstrap-3.git#1.1",
    "nouislider": "^8.5.1",
    "partition-bundle": "^2.5.0",
    "redux": "^3.5.2",
    "requirejs": "^2.2.0",
    "riot": "^2.5.0",
    "riot-ts": "git://github.com/tfsimondouglas/riot-ts.git",
    "tf-modernizr": "git://github.com/tomorrowfinance/tf-modernizr.git",
    "webshim": "^1.15.10",
    "wnumb": "git://github.com/tannerhodges/wnumb"
  },
  "scripts": {
    "test": "protractor protractor.conf.js",
    "postinstall": "node node_modules/.bin/gulp --production",
    "watch": "node node_modules/.bin/gulp watch",
    "gulp": "node node_modules/.bin/gulp",
    "kill": "for pid in `ps -ef | grep gulp | awk '{print $2}'` ; do kill -9 $pid ; done",
    "start": "npm run watch",
    "restart": "npm run kill & npm start",
    "build": "node node_modules/.bin/gulp --production"
  }
}

Example call in app.ts, which barfs:

let { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
console.log(x); // 1
console.log(y); // 2
console.log(z); // { a: 3, b: 4 }

// Spread properties
let n = { x, y, ...z };
console.log(n); // { x: 1, y: 2, a: 3, b: 4 }

14:39:26] Starting 'all'... [14:39:26] Starting 'browserify'... Error TS1180: Property destructuring pattern expected. Error TS1136: Property assignment expected.

While I didn't have your problem, I had a different problem where I was getting babel returning undefined, until I called it inside the function scope. Perhaps it gets binded late?

elixir(function (mix) {

// modify elixir.config.js.browserify.transformers  here

.
.
.
  mix.browserify('vue.js')