Migrating

Underscore

When migrating from Underscore to Lodash there are several differences to be aware of.
Below are some of the ones that stand out. For a more thorough guide check out lodash-codemods, eslint-plugin-lodash & Underscore to Lodash Converter.

• Underscore _.any is Lodash _.some
• Underscore _.all is Lodash _.every
• Underscore _.compose is Lodash _.flowRight
• Underscore _.contains is Lodash _.includes
• Underscore _.each doesn’t allow exiting by returning false is Lodash _.forEach
• Underscore _.escape escapes backtick characters ('`'), while Lodash does not
• Underscore _.findWhere is Lodash _.find
• Underscore _.flatten is deep by default while Lodash is shallow
• Underscore _.groupBy's iteratee receives the arguments value, indexNumber, and originalCollection, while Lodash _.groupBy's iteratee receives only the argument value
• Underscore _.indexOf with 3rd parameter undefined is Lodash _.indexOf
• Underscore _.indexOf with 3rd parameter true is Lodash _.sortedIndexOf
• Underscore _.indexBy is Lodash _.keyBy
• Underscore _.invoke is Lodash _.invokeMap
• Underscore _.mapObject is Lodash _.mapValues
• Underscore _.max combines Lodash _.max & _.maxBy
• Underscore _.min combines Lodash _.min & _.minBy
• Underscore _.sample combines Lodash _.sample & _.sampleSize
• Underscore _.object combines Lodash _.fromPairs and _.zipObject
• Underscore _.omit by a predicate is Lodash _.omitBy
• Underscore _.pairs is Lodash _.toPairs
• Underscore _.pick by a predicate is Lodash _.pickBy
• Underscore _.pluck is Lodash _.map
• Underscore _.sortedIndex with an iteratee is Lodash _.sortedIndexBy, which doesn't take a 4th (context) parameter.
• Underscore _.uniq by an iteratee is Lodash _.uniqBy. _.uniq with the isSorted parameter = true is Lodash _.sortedUniq (or Lodash _.sortedUniqBy when using an iteree).
• Underscore _.unique alias for _.uniq does not exist in Lodash
• Underscore _.where is Lodash _.filter
• Underscore _.isFinite doesn’t align with Number.isFinite
  (e.g. _.isFinite('1') returns true in Underscore but false in Lodash)
• Underscore _.matches shorthand doesn’t support deep comparisons
  (e.g. _.filter(objects, { 'a': { 'b': 'c' } }))
• Underscore ≥ 1.7 & Lodash _.template syntax is
  _.template(string, option)(data)
• Lodash _.memoize caches are Map like objects
• Lodash doesn’t support a context argument for many methods in favor of _.bind
• Lodash supports implicit chaining, lazy chaining, & shortcut fusion
• Lodash split its overloaded _.head, _.last, _.rest, & _.initial out into
  _.take, _.takeRight, _.drop, & _.dropRight
  (i.e. _.head(array, 2) in Underscore is _.take(array, 2) in Lodash)

Backbone

Lodash works great with Backbone. It’s even run against Backone’s unit tests on every commit.
You can replace Underscore with Lodash in Backbone by using an AMD loader, browserify, or webpack.

Note: Lodash v4 works with Backbone ≥ v1.3.0.

• Using AMD “paths” configuration

require({
  'paths' {
    'backbone': 'path/to/backbone',
    'jquery': 'path/to/jquery',
    'underscore': 'path/to/lodash'
  }
}, ['backbone'], function(Backbone) {
  // use Backbone
});

• Using the aliasify transform for browserify by adding a section to your package.json

{
  "browserify": {
    "transform": ["aliasify"]
  },
  "aliasify": {
    "aliases": {
      "underscore": "lodash"
    }
  }
}

and executing browserify with the aliasify parameter

$ browserify entry.js --global-transform aliasify -o out.js

• Using the resolve.alias configuration in webpack

module.exports = {
  'resolve': {
    'alias': {
      'underscore': 'absolute/path/to/lodash'
    }
  }
};