Deep-merge the values of one object structure into another. Similar to Object.assign() except it processes the full depth of the object structure, not only the top level. Useful for merging config.

import deepMerge from '@75lb/deep-merge'

Typical example merging four objects. Input:

deepMerge(
  { port: 8000, data: { animal: 'cow' } },
  { stack: ['one'] },
  { stack: ['two'], help: true },
  { data: { animal: 'bat', metal: 'iron' } }
)

Result

{
  port: 8000,
  stack: ['two'],
  help: true,
  data: { animal: 'bat', metal: 'iron' }
}

Empty arrays are ignored and not merged in. Input:

deepMerge(
  { stack: ['one'] },
  { stack: [] }
)

Result:

{ stack: ['one'] }

However, if the later array contains one or more values the later array will replace the original:

deepMerge(
  { stack: ['one'] },
  { stack: ['two'] }
)

Result:

{ stack: ['two'] }

This library is compatible with Node.js, the Web and any style of module loader. It can be loaded anywhere, natively without transpilation.

Within a Node.js ECMAScript Module:

import deepMerge from '@75lb/deep-merge'

Within an modern browser ECMAScript Module:

import deepMerge from './node_modules/@75lb/deep-merge/dist/index.mjs'

© 2021 Lloyd Brookes <75pound@gmail.com>.

Tested by test-runner. Documented by jsdoc-to-markdown.