_.deepExtend ·

A deep extend implementation with added sugar for underscore, lodash and friends.

Based conceptually on the _.extend() function in underscore.js.

Installation:

npm install underscore-deep-extend

Dependency:

One of

• underscore.js
• lodash.js
• another clone that provides _.each, _.is(Array|Date|Null|Object|String|Undefined), _.clone and _.reject.

Usage:

Load it, either as is (in the browser), as an AMD module, or as a CommonJS/Node.js module), then mix it in with the parent library (which must be explicitly injected):

_.mixin( { deepExtend: underscoreDeepExtend( _ ) } )

Call it like this:

const myObj = _.deepExtend( grandparent, child, grandchild, greatgrandchild )

Or this:

_.deepExtend( myObj, child, grandchild, greatgrandchild )

Notes

Keep it DRY.

This function is especially useful if you're working with JSON config documents. It allows you to create a default config document with the most common settings, then override those settings for specific cases. It accepts any number of objects as arguments, giving you fine-grained control over your config document hierarchy.

Special Features and Considerations:

• parentRE allows you to concatenate strings. example:

  const obj = _.deepExtend( { url: "www.example.com" }
                          , { url: "http://#{_}/path/to/file.html" } 
                          )
  
  console.log( obj.url )

  output: http://www.example.com/path/to/file.html

• parentRE also acts as a placeholder, which can be useful when you need to change one value in an array, while leaving the others untouched. example:

  const arr = _.deepExtend( [ 100,    { id: 1234 }, true,  "foo",  [ 250, 500] ]
                          , [ "#{_}", "#{_}",       false, "#{_}", "#{_}" ]
                          )
  console.log( arr )

  output: [ 100, { id: 1234 }, false, "foo", [ 250, 500 ] ]

• The previous example can also be written like this:

  const arr = _.deepExtend( [ 100,    { id: 1234 }, true,  "foo",  [ 250, 500 ] ]
                          , [ "#{_}", {},           false, "#{_}", [ ] ]
                          )
  console.log( arr )

  output: [ 100, { id: 1234 }, false, "foo", [ 250, 500 ] ]

• And also like this:

  const arr = _.deepExtend( [ 100,    { id: 1234 }, true, "foo", [ 250, 500 ] ]
                          , [ "#{_}", {},           false ]
                          )
  console.log( arr )

  output: [ 100, { id: 1234 }, false, "foo", [ 250, 500 ] ]

• Array order is important. example:

  const arr = _.deepExtend( [ 1, 2, 3, 4 ]
                          , [ 1, 4, 3, 2 ]
                          )
  
  console.log( arr )

  output: [ 1, 4, 3, 2 ]

• You can remove an array element set in a parent object by setting the same index value to null in a child object. Example:

  const obj = _.deepExtend( { arr: [ 1,      2,   3, 4 ] }
                          , { arr: [ "#{_}", null ] }
                          )
  
  console.log( obj.arr )

  output: [ 1, 3, 4 ]

License

Copyright (C) 2012-2017 Kurt Milam - http://xioup.com

License: MIT

Original source: https://gist.github.com/1868955