JavaScript ES6 - simple deep copy routine (does not handle circular references) MIT License

deepCopy.js

// deepCopy.js
// simple deep copy routine
// does not handle circular references
// (C) 2017, Richard Marks. MIT License
// ccpsceo@gmail.com http://www.ccpssolutions.com

// use:
// const { deepCopy, runTests } = require('./deepCopy')
// const clone = deepCopy(source)
//
// quick test:
// const { deepCopy, runTests } = require('./deepCopy')
// runTests()

const deepCopy = source => {
  if (source === undefined || source === null) {
    return undefined
  } else if (Array.isArray(source)) {
    return source.map(element => deepCopy(element))
  } else if (typeof source === 'object') {
    const clone = Object.create({})

    for (prop of Object.keys(source)) {
      clone[prop] = deepCopy(source[prop])
    }
    
    return clone
  } else if (typeof source === 'string' || source.constructor === String) {
    return `${source}`
  } else {
    return source
  }
}

const runTests = () => {
  const assert = (name, desc, condition) => {
    return new Promise((resolve, reject) => {
      condition && resolve({ name, desc })
      !condition && reject(new Error(`Assertion Failed: ${name} ${desc} is false`))
    })
  }

  const source = {
    child: {
      grandchild: [
        {
          name: 'bobby'
        },
        {
          name: 'matt'
        }
      ]
    }
  }

  const clone = deepCopy(source)

  clone.child.grandchild[0].name = 'angela'
  clone.child.grandchild.push({ name: 'johnny' })

  assert(
    'modifying clone does not modify original',
    'clone.child.grandchild[0].name !== source.child.grandchild[0].name',
    clone.child.grandchild[0].name !== source.child.grandchild[0].name
  )
  .catch(err => console.error(err))
  .then(({ name, desc }) => {
    console.log(`Assertion Passed: ${name} ${desc} is true`)
    console.log(JSON.stringify(source, null, 2))
    console.log(JSON.stringify(clone, null, 2))
  })
}

module.exports = {
  deepCopy,
  runTests
}