Object.assign Polyfill example with Babel 6

Babel-6-polyfill-example.md

Showcasing how Babel 6 includes unnecessary polyfill code

step-1-create-app.sh

mkdir babel-6-app
cd babel-6-app
mkdir src
npm init -y
npm install --save-dev babel-cli babel-preset-env babel-polyfill
touch .babelrc
touch src/index.js

step-2-babelrc

{
  "presets": [
    [
      "env", {
        "targets": {
          "browsers": ["ie >= 9", "safari >= 7"]
        },
        "useBuiltIns": "usage"
      }
    ]
  ]
}

step-3-index.js

import "babel-polyfill";

const backendResponse = [
  { title: '', timestamp: '1960-04-15T18:34:38+05:00' },
  { title: '', timestamp: '2007-05-15T18:34:38+05:00' }
];

const timeline = backendResponse.map(event => {
  const date = new Date(event.timestamp).toLocaleDateString('en-US');
  return Object.assign(event, { date }); // <=
});

console.log('timeline', timeline);

step-4-run-babel.sh

npx babel src --out-dir lib

step-5-output.js

'use strict';

require('core-js/modules/es6.typed.array-buffer');

require('core-js/modules/es6.typed.data-view');

require('core-js/modules/es6.typed.int8-array');

require('core-js/modules/es6.typed.uint8-array');

require('core-js/modules/es6.typed.uint8-clamped-array');

require('core-js/modules/es6.typed.int16-array');

require('core-js/modules/es6.typed.uint16-array');

require('core-js/modules/es6.typed.int32-array');

require('core-js/modules/es6.typed.uint32-array');

require('core-js/modules/es6.typed.float32-array');

require('core-js/modules/es6.typed.float64-array');

require('core-js/modules/es6.map');

require('core-js/modules/es6.set');

require('core-js/modules/es6.weak-map');

require('core-js/modules/es6.weak-set');

require('core-js/modules/es6.reflect.apply');

require('core-js/modules/es6.reflect.construct');

require('core-js/modules/es6.reflect.define-property');

require('core-js/modules/es6.reflect.delete-property');

require('core-js/modules/es6.reflect.get');

require('core-js/modules/es6.reflect.get-own-property-descriptor');

require('core-js/modules/es6.reflect.get-prototype-of');

require('core-js/modules/es6.reflect.has');

require('core-js/modules/es6.reflect.is-extensible');

require('core-js/modules/es6.reflect.own-keys');

require('core-js/modules/es6.reflect.prevent-extensions');

require('core-js/modules/es6.reflect.set');

require('core-js/modules/es6.reflect.set-prototype-of');

require('core-js/modules/es6.promise');

require('core-js/modules/es6.symbol');

require('core-js/modules/es6.object.freeze');

require('core-js/modules/es6.object.seal');

require('core-js/modules/es6.object.prevent-extensions');

require('core-js/modules/es6.object.is-frozen');

require('core-js/modules/es6.object.is-sealed');

require('core-js/modules/es6.object.is-extensible');

require('core-js/modules/es6.object.get-own-property-descriptor');

require('core-js/modules/es6.object.get-prototype-of');

require('core-js/modules/es6.object.keys');

require('core-js/modules/es6.object.get-own-property-names');

require('core-js/modules/es6.object.assign');

require('core-js/modules/es6.object.is');

require('core-js/modules/es6.object.set-prototype-of');

require('core-js/modules/es6.function.name');

require('core-js/modules/es6.string.raw');

require('core-js/modules/es6.string.from-code-point');

require('core-js/modules/es6.string.code-point-at');

require('core-js/modules/es6.string.repeat');

require('core-js/modules/es6.string.starts-with');

require('core-js/modules/es6.string.ends-with');

require('core-js/modules/es6.string.includes');

require('core-js/modules/es6.regexp.flags');

require('core-js/modules/es6.regexp.match');

require('core-js/modules/es6.regexp.replace');

require('core-js/modules/es6.regexp.split');

require('core-js/modules/es6.regexp.search');

require('core-js/modules/es6.array.from');

require('core-js/modules/es6.array.of');

require('core-js/modules/es6.array.copy-within');

require('core-js/modules/es6.array.find');

require('core-js/modules/es6.array.find-index');

require('core-js/modules/es6.array.fill');

require('core-js/modules/es6.array.iterator');

require('core-js/modules/es6.number.is-finite');

require('core-js/modules/es6.number.is-integer');

require('core-js/modules/es6.number.is-safe-integer');

require('core-js/modules/es6.number.is-nan');

require('core-js/modules/es6.number.epsilon');

require('core-js/modules/es6.number.min-safe-integer');

require('core-js/modules/es6.number.max-safe-integer');

require('core-js/modules/es6.math.acosh');

require('core-js/modules/es6.math.asinh');

require('core-js/modules/es6.math.atanh');

require('core-js/modules/es6.math.cbrt');

require('core-js/modules/es6.math.clz32');

require('core-js/modules/es6.math.cosh');

require('core-js/modules/es6.math.expm1');

require('core-js/modules/es6.math.fround');

require('core-js/modules/es6.math.hypot');

require('core-js/modules/es6.math.imul');

require('core-js/modules/es6.math.log1p');

require('core-js/modules/es6.math.log10');

require('core-js/modules/es6.math.log2');

require('core-js/modules/es6.math.sign');

require('core-js/modules/es6.math.sinh');

require('core-js/modules/es6.math.tanh');

require('core-js/modules/es6.math.trunc');

require('core-js/modules/es7.array.includes');

require('core-js/modules/es7.object.values');

require('core-js/modules/es7.object.entries');

require('core-js/modules/es7.object.get-own-property-descriptors');

require('core-js/modules/es7.string.pad-start');

require('core-js/modules/es7.string.pad-end');

require('core-js/modules/web.timers');

require('core-js/modules/web.immediate');

require('core-js/modules/web.dom.iterable');

require('regenerator-runtime/runtime');

var backendResponse = [{ title: '', timestamp: '04-15-1960T18:34:38+0500' }, { title: '', timestamp: '05-15-2007T18:34:38+0500' }];

var timeline = backendResponse.map(function (event) {
  var date = new Date(event.timestamp).toLocaleDateString('en-US');
  return Object.assign(event, { date: date }); // <=
});

console.log('timeline', timeline);