Hash Tables - Beau teaches JavaScript

[@lenaggar]

@Beau thank you for what you do for the community

[@arthuretf]

Shouldn't it be `i < storage[index].length` on line 46?

[@BeauCarnes]

Yup! I fixed it in the code that is linked to in the description.

[@__abshir]

line 45*

[@funkybuddha1598]

I wasted 2 hours because of that!

[@NathanielBabalola]

On line 30, you're overwriting the previous value that was tied to that key. Is that how it's meant to be ?

[@dcts7526]

was looking for that comment. Since the hashfunction is deterministic, the same key will always result in the same index, hence the value must be by definition the same. Overriding it is unneccessary you are right!

[@jhovahngibbs6720]

tux is a penguin, that made me smile

hey, good video

[@chavychaze9366]

awful explanation, awful. Why make such an easy topic so hard?

[@fatemabohra4277]

there is no such video except this which explains a simple hash function in javascript in a practical way.

[@shayanjavadi]

Really weird mixture of var let and const here. Your storage can be a const since the array location in the memory doesn't change, only the array items do. all the functions should also be consts as well. there's really no point in using var anymore. great video otherwise!

[@camillemorell3270]

This is the best video I've watched on Hash Tables

[@paschalynukwuani6930]

Beau you are one of the best tutors on the internet.

[@goodrowj]

I think I might be missing something here, wasn't the point of a hastable to have O(1) reads, inserts, and deletes? This is running O(n) blocks for each of those operations. Is there a way to get those down to O(1) in Javascript?

[@ernwillburn]

Yeah this video is not really correct or O(1)

[@dannytran4667]

You get constant time by reducing the chance of collision. One simple way to do this is to double your storage size when the load factor gets high (the ratio of items to buckets). When you hit the load factor, double the number of buckets (in this case the storage Limit) and rehash all the items so hopefully they're in their own bucket.

[@seyfullah7314]

Average time complexity of finding the hash value of any input is already O(n), However, how come the average time complexity of insertion be O(1) ?

[@NathanielBabalola]

The buckets in the hashtable function is 4, but you're using 10 in the hash function ?

[@bluemenkranz_2953]

actually iam a beginner but when i reading the code for add function i got confused and i try to fix it with this code instead > this.add = function (key, value) { var index = hash(key, storageLimit); if (storage[index] === undefined) { storage[index] = [key, value]; } else { storage[index].push([key, value]); } }; still work tho

[@bruhmoment3731]

hello Genshin player.

[@goodwish1543]

Nice explanation. Good work, Beau Carnes ! Line 42, There is a use case in Remove method, that is the key doesn't exist in array. The code logic works. If we may test it separately, it'll be more clear.

[@vishalheble]

Can you explain what do you mean by "When (inserted=== false), then push the key,vales into storage array. But how do we get multiple entries for the same bucket? It means collision right? But how can it happen when you don't find the same key which actually happens in previous case i.e. when the key exists already. Help me.

[@sergeypomaraiko4661]

at line 43 you have deleted array item, but length of array wasn't changed. So line 42 never will be true if we have inserted item once

[@facundomartingarciaengel6318]

U re the best bro ;) thanks from Argentina!

[@OliverMensahDev]

Good work Sir

[@JohnDoe-ji1zv]

Is hashtable actually used in a daily programming ? Could you give an example please

[@kattenelvis1778]

No it's only used in leetcode and interview questions.

[@RedEyedJedi]

It is used anytime you want a fast insertion, look up or delete. The data structure you decide to use should always be based on how the data is going to be used. Don't just use an array for everything, although an array can be used for most things, speed is a major factor in developing software.

[@dcts7526]

Good question, would be interested to hear too. We all use hashtables indirectly by using hashmaps, sets or simply objects. But I've never applied a hashtable throughout my developer career so far too...

[@sabuein]

Thank you.

[@greendsnow]

what?

[@ChocolateMilkCultLeader]

So well done

[@aaronargottelopez3488]

Thanks

[@anirvanchandra]

which text editor do you use

[@rexromae17]

that looks like CodePen

[@FernandoFleuryGil]

it's a website called codepen

[@sifatmoonjerin2479]

Hey, great content! But I think using splice instead of delete will be a better solution. This throws an error if you remove a chained key and then try to reassign it.

[@BrasilEmFatos]

hmm, but I think splice gonna remove the slot spaces in our storage, while delete keeps the space associated with that index but with an undefined value.