JS COLLECTIONSChapter 4 · JS Collections Depth

Sorting Arrays

array.sort() sorts in place and, by default, compares items as strings, so [10, 9, 1].sort() gives [1, 10, 9]. Pass a compare function to sort properly: (a, b) => a - b sorts numbers ascending, (a, b) => b - a descending, and a.name.localeCompare(b.name) sorts text alphabetically. Copy first with [...arr] when you need to keep the original order.

Worked example

How it reads

Without a compare function, numbers are sorted as text
A negative result puts a first, a positive result puts b first
Objects sort by whatever the compare function compares

Common mistakes

sort() changes the original array. Copy it first if other code still needs the old order.

Cloud tip: Always pass a compare function when sorting numbers. It is one of the most common JavaScript bugs.