The other day at work I was faced with what I think is a rather common problem when dealing with data coming from an API.
I was getting from my as...
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Without getting into cryptic one-liners, there's a pretty straight forward linear time solution as well.
Hey Matt, nice solution! Yeah, all ways leads to Rome :)
Well... yes and no.
I feel it's important to distinguish that the OP-s solution loops over the whole array twice. I know there are times to make a trade-off between performance and readability, but I don't feel this needs to be one of those times :)
Great answer, thank you Matt!
wow crazy matt
thanks for this
Here's another possibility using the
Map
class constructor andvalues
method:I have to create an account and say thank you! This answer save my day.
Thanks !!
wow, i love that
Interesting challenge. So I've three very similar solutions. They are all based on the same principle of reducing the array into a key-value structure and re-creating the array from the values only.
Approach 1: Classical Reducer
(reducer maintains immutability)
Depending on your array size, this approach might easily become a bottleneck in your app. More performant is to mutate your accumulator object directly in the reducer.
Approach 2: Reducer with object-mutation
The larger your input array, the more performance gain you'll have from the second approach. In my benchmark (for an input array of length 500 - with a duplicate element probability of 0.5), the second approach is ~440 x as fast as the first approach.
Approach 3: Using ES6 Map
My favorite approach uses a map, instead of an object to accumulate the elements. This has the advantage of preserving the ordering of the original array:
Using the the same benchmark conditions as above, this approach is ~2 x as fast as the second approach and ~900 x as fast as the first approach.
Conclusion
Even if all three approaches are looking quite similar, they have surprisingly different performance footprints.
You'll find the benchmarks I used here: jsperf.com/uniq-by-prop
Hi ! One other one line path to Rome, from France :
`
Merci! :)
More JS but too slow.
I have also this solution O.o
But this only works with
address.id
, so this doesn't work withaddress.name
Really, why this doesn't work like that?
Well, you're passing
[address.id]
as an index to thedupAddress
array, that's just not going to work because theid !== index
. Try changing it toaddress.id
oraddress.name
without accessing the arrayOkay, I tried it didn't work actually I was wonder why that didn't work. Thanks.
I found myself with this issue recently and though I've always used the same code to find distinct primitives (before we had the
Set
object), this code required me to adhere to the C# API where you pass in a comparison functionT -> T -> boolean
. This solution felt relatively clean though obviously not in linear time.github.com/jreina/ShittyLINQ.js/bl...
let array = [];
let singleEle = [];
const arr = [
{ id: 1, {questionId : { _id: "5e2016a1560d8c2aa842e65d"} }},
{ id: 1, {questionId : { _id: "5e1c211cc201f33834e7baf1"} }},
{ id: 1, {questionId : { _id: "5e201733560d8c2aa842e65e"} }}
];
arr.forEach(item => {
if (array[item.questionId._id] ) {
}
else{
array[item.questionId._id] = true;
singleEle.push(item)
}
});
Thanks for the code snippet, Marina...I'm getting to errors when I attempt to use it. The first is "Set is only referred to a type but is being used as a value here"
when I use the "REDUCE" example I get the following in the console:
Maximum call stack size exceeded
at Array.reduce
Really enjoyed this article and the rad discussion!!!!!!
Thanks so much for your article. It saved and made my day. :)
This is great! Thanks
The array reduce solution saved my day!
Tanx Marina
Welcome! :D
what does this bit do? not sure I understand? -> acc.concat([current])
Array.concat is a way to concatenate two arrays into one.
developer.mozilla.org/en-US/docs/W...
Thanks! This is exactly what I was looking for