The for...of Loop

In short: for (const value of iterable) hands you each value directly, one at a time, with no index and no counting. It works on any iterable — arrays, strings, Maps, Sets — because each of those defines how to hand out its items in order. It does not work on a plain object, which has no built-in order to iterate, and throws a TypeError if you try.

Printing every song, no counting required

When you don't need the position, for...of is the cleanest way to visit every item:

Compare this with a for loop that needs songs[i] and an index variable you never actually use — for...of hands you the song directly.

Walking a string, and a Map's entries

for...of isn't just for arrays — it works on anything iterable:

A string hands out one character per lap. A Map hands out [key, value] pairs, which the loop destructures straight into title and count — no .get() calls needed.

The object that isn't iterable

The trap: a plain object looks like it should work, but doesn't.

Arrays, strings, Maps and Sets all define an iterator — a built-in way to hand out their contents in order. A plain object doesn't, so for...of has nothing to walk and throws a TypeError. To loop over an object's own properties, use for...in (next lesson) or Object.entries(song), which turns it into an iterable array of pairs.

Quick practice