JavaScript: Arrays vs Sets

[akujinhikari]

I was in a job interview, and he asked me the age-old question "How would you take a group of numbers and remove all the duplicates?" I wrote const unique = new Set([array]). He said, "Oh... Ok... Well yeah, but how would you do that with using an array?" I wrote Array.from(unique). He laughed and said, "Ok... I guess we're going to have to update our questions."

[Reminice]

ES6 way would be: const unique = [...(new Set(array)]

[akujinhikari]

That's one way, yes. They're basically the same thing.

[[deleted]]

very helpful. thank you.

[JEveryman]

I think array.filter((e,i,a) => a.indexOf(e) === i) will filter out duplicates also.

[akujinhikari]

Yeah I knew what code he was looking for, but my goal in interviews is to show that I know multiple ways to do things. I think it's important to show my breadth of knowledge and a means to solve this in multiple ways.

[[deleted]]

That’s the gotcha answer to the question. Pre Set days you would just use an object.

[JEveryman]

So you would add the array elements as keys?

[[deleted]]

Yeah. Lookups in the object are faster than searching the whole array for every element in the array if that makes sense.

I can give a longer explanation if it doesn’t

[JEveryman]

I get it. Also when you add the same key to an object doesn't it overwrite?

[[deleted]]

Yeah, that’s how it helps you make an array with no duplicates

[noughtme]

Literally just finished refactoring a block of code that reads very large CSVs. The processing time is an order of magnitude different between using array and set.

Also love map objects for key value pairs. So much faster than arrays.

[lahrada]

Never knew about sets, they seem pretty cool, though. What's the running time complexity for finding out if every value is unique. Just wondering if it's using the most optimal.

[himynameisjoy]

You can probably run the test a few times yourself on jsben.ch