.gitignore

node_modules

package.json

{
  "name": "clone-speed-tests",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "cross-env NODE_ENV=production node run.js | tee results.md"
  },
  "keywords": [],
  "author": "J. Harshbarger",
  "license": "MIT",
  "dependencies": {
    "babyparse": "^0.4.6",
    "chuhai": "^1.2.0",
    "cross-env": "^2.0.1",
    "isomorphic-fetch": "^2.2.1",
    "lodash": "^4.15.0",
    "microtime": "^2.1.1",
    "platform": "^1.3.1"
  },
  "xo": {
    "semicolon": true,
    "esnext": true,
    "space": 2,
    "plugins": []
  },
  "devDependencies": {
    "xo": "^0.16.0"
  },
  "repository": {
    "type": "git",
    "url": "git+ssh://git@gist.github.com/d6bacd4ce0d5835b801ba028f9b1c81b.git"
  },
  "bugs": {
    "url": "https://gist.github.com/d6bacd4ce0d5835b801ba028f9b1c81b"
  },
  "homepage": "https://gist.github.com/d6bacd4ce0d5835b801ba028f9b1c81b",
  "description": ""
}

results.md

Node.js 6.3.1 on Darwin 64-bit

clone

.map + Object.assign Polyfill (without checks) x 759 ops/sec ±4.79% (11 runs sampled)
.map + Object.assign Polyfill x 720 ops/sec ±7.29% (11 runs sampled)
.map + Object.assign x 474 ops/sec ±4.80% (11 runs sampled)
.map + lodash.assign x 300 ops/sec ±6.55% (11 runs sampled)
.map + lodash.clone x 227 ops/sec ±7.44% (11 runs sampled)
JSON string/parse x 219 ops/sec ±10.27% (10 runs sampled)
lodash.cloneDeep x 146 ops/sec ±14.54% (11 runs sampled)

Fastest is .map + Object.assign Polyfill (without checks), .map + Object.assign Polyfill

run.js

const assert = require('assert');
const lodash = require('lodash');
const suite = require('chuhai');
const Baby = require('babyparse');
const platform = require('platform');
const fetch = require('isomorphic-fetch');

/* const gz = fs.readFileSync('h1bs.csv.gz');
const text = zlib.gunzipSync(gz);
const data = Baby.parse(String(text), {
  header: true,
  delimiter: ',',
  skipEmptyLines: true
}).data.slice(0, 5000); */

console.log(`# ${platform.description}\n`);

suite.cb('clone', s => {
  s.set('maxTime', 0.1);
  s.set('minSamples', 10);

  let copy = null;
  let data = null;

  s.cycle(() => {
    assert(copy !== null);
    assert(copy !== data);
    assert(copy[0] !== data[0]);
    assert.deepStrictEqual(copy, data);
    copy = null;
  });

  s.bench('lodash.cloneDeep', () => {
    copy = lodash.cloneDeep(data);
  });

  s.bench('.map + lodash.clone', () => {
    copy = data.map(d => lodash.clone(d));
  });

  s.bench('.map + lodash.assign', () => {
    copy = data.map(d => lodash.assign({}, d));
  });

  s.bench('JSON string/parse', () => {
    copy = JSON.parse(JSON.stringify(data));
  });

  s.bench('.map + Object.assign', () => {
    copy = data.map(d => Object.assign({}, d));
  });

  s.bench('.map + Object.assign Polyfill', () => {
    copy = data.map(d => objectAssignPolyfill({}, d));
  });

  s.bench('.map + Object.assign Polyfill (without checks)', () => {
    copy = data.map(d => objectAssignPolyfillYOLO({}, d));
  });

  return fetch('http://swizec.github.io/h1b-software-salaries/data/h1bs.csv')
   .then(response => {
     if (response.status >= 400) {
       throw new Error('Bad response from server');
     }
     return response.text();
   })
   .then(text => {
     data = Baby.parse(text, {
       header: true,
       delimiter: ',',
       skipEmptyLines: true
     }).data.slice(0, 1000);
     s.run();
   });
});

// from https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
function objectAssignPolyfill(target) {
  'use strict';
  // We must check against these specific cases.
  if (target === undefined || target === null) {
    throw new TypeError('Cannot convert undefined or null to object');
  }

  const output = Object(target);
  for (let index = 1; index < arguments.length; index++) {
    const source = arguments[index];
    if (source !== undefined && source !== null) {
      for (const nextKey in source) {
        if (Object.prototype.hasOwnProperty.call(source, nextKey)) {
          output[nextKey] = source[nextKey];
        }
      }
    }
  }
  return output;
}

function objectAssignPolyfillYOLO(output, source) {
  for (const nextKey in source) {
    if (Object.prototype.hasOwnProperty.call(source, nextKey)) {
      output[nextKey] = source[nextKey];
    }
  }
  return output;
}