Lodash Migration

Migrate from Lodash to ES6/ES7 features

Starting from Mixxx 2.5.0, the embedded lodash.mixxx.js library is deprecated and planned for removal in Mixxx 2.6.0. This document is here to help controller maintainers migrate from Lodash functions to ES6/ES7 new features.

_.assign

_.assign can simply be replaced by Object.assign.

_.merge

_.merge works like _.assign except it recursively merge two objects. Such a use case is currently unknown in Mixxx controllers. However, if you have a valid use case for _.merge, don't hesitate to open an issue describing it.

_.forEach

_.forEach can transparantly be replaced by Array.prototype.forEach when using an Array, a Map and other common containers and for … of for most of other Js iterables.

A key/value pair iteration over objects is also achivable using Object.entries and Map.prototype.entries:

const opts = {
   var1 : "Test",
}

Object.entries(opts).forEach(([k, v]) => {
  // do something here
});

const map = new Map([
  [1, "un"],
  [2, "deux"],
  [3, "trois"],
]);

map.forEach((k, v) => {
  // do something here
});

_.map

For Array's, _.mapcan transparently be replaced by Array.prototype.map in most cases:

[1, 2, 3].map(it => it + 1);

_.filter

_.filter can be replaced by Array.prototype.filter for Array and Object.entries(obj).filter:

[1, 2, 3, 4, 5].filter(it => it % 2 === 0);

Object.entries({
  midi: [], deckNum: 1
}).filter(
  ([k, v]) => Number.isInteger(v)
);

Sparse Arrays

When instanciating an Array, using the constructor, _.map, _.filter and _.forEach work differently than their Array.prototype counterparts on sparse arrays.

let arr = Array(4);
// [ <4 empty items> ]
_.map(arr, (_elem, i) => i);
// [ 0, 1, 2, 3 ]
arr.map((_elem, i) => i)
// [ <4 empty items> ]

In most cases, it's better to instanciate and initialize the Array in the same expression using []. In particularly large arrays, you can use the fact that Array.prototype.fill does not ignore empty items to initalize the array with some value and then iterate over that (eg Array(16).fill(0).map(...)).

Other?

The function above are the one typically used in official controllers. If you have another usecase, don't hesitate to open an issue so we can documnent it here.