Array map, filter, reduce, forEach
Comes up in: Coding
This concept is being written. It gets the full five steps — explanation, predict, interview angle, practice with tests, and review cards. Here is exactly what it will cover, so you can study it elsewhere in the meantime.
What it covers
- callback arguments (value, index, array)
thisArg- sparse arrays (holes skipped)
- reduce without initial value and empty array TypeError
Words you will know
What you will practise
- implement four methods
Interview questions this answers
- Write a polyfill for
Array.prototype.reduce. What happens with an empty array and no initial value?