Notes for the Data Transformation problems

data-transformation-notes.md

Data transformations

Essential Array Methods

These are the JS Array methods that should be your go-to tools for everything. They're the building blocks of some extremely powerful combinations of algorithmic logic.

Prototype methods (methods called on an instance of an Array)

• [].reduce: The king of the array methods; nearly all array methods can be derived from reduce. Learn it and get really good at using it.
• [].map
• [].filter
• [].includes
• [].every
• [].some
• [].slice

Static methods (methods called on the Array constructor directly)

• Array.isArray
• Array.of
• Array.from

Irrelevant Array Methods

These are the Array methods that are fine to use, and at one point were used all the time, but they have since been made irrelevant by new JS language features.

• [].indexOf Use includes instead
• [].concat Use the spread operator instead

Banned Array Methods

These the JS Array methods that should be avoided and ideally removed from your vocabulary. They either encourage imperative code or, even worse, they mutate state.

• [].forEach: Imperative code enabler
• [].pop: Mutates
• [].push: Mutates
• [].splice: Mutates
• [].shift: Mutates
• [].unshift: Mutates