No, its not. The length property shouldn't work that way, it should be a read property, never a write property. Any other type of behavior on this property, which alters its content, is a language malfunction and should be corrected in the future. There are too many cases like this that have not been fixed because too many programmers have gotten used to these bad practices, and as a result we have an inconsistent language with countless bugs, exceptions, and inconsistent behaviors.
@@ky3ow of course, that is why there are migration processes from obsolete to current functionalities. Every language goes through that process and that's why there are different versions.
I mean the effects make sense, and could even be useful, however you should not be able to change the value of arr.length. It should obviously be read only.
@@poopfartlord9695Its probably unlogical for people used to say C where it works different. But in JS a array is not really the same thing as an array in C. one position in the array in Javascript takes up like tenths of bytes of memory. Already there we should understand that its not a normal array. Index 0 and Index 1 does not need to be saved next to eachother in Javascript memory. Its more of a linked list / hashtable behind the scenes. Thats why you can do things like this. I think its brilliant, and I dont care if some old law from 70ies programming think its wrong :)
@@kumarraj197 We are actually too much used to the restrictions provided in C/C++. There's too much leniency in datatypes or array length in Javascript.
the empty items are just properties on the array that dont even exist, thats why theyre not undefined but return undefined when you index them just like an object key
I never faced the use case where I had to set an array's length and fill it with empty values. Usually length is a trivial value that reflects how many items are left.
Under the hood the array has to reserve memory. You can either reallocate the memory at ever add OR right aways allocate memory for e.g. 10 elements and then simply set them, which is supposing to be faster. The problem with script "kiddies" is: they never learn how this is ACTUALLY being implemented under the hood. If you learn programming in C or PASCAL you would understand that a collection either needs to dynamically allocate and move memory or use something like linked lists. Linked lists don't require reallocation but are SLOW. Continuous memory (array) is very fast but if you if you want an element that will require to grow the allocated memory this is costly. So typically a strategy to implement this to allocate more memory right away to avoid reallocation. In C#: arrays are fixed size. List has an option to specify a capacity but the size is dynamic (and internally a list is implemented as an array).
How does this really explain why some items are undefined instead of adding to the last possible item location or simply length is read property and there’s another write property like all other languages almost ?? Thus being said if I have an array of undefined how to get rid of all the undefined in an efficient way ? Let’s say I have [ “a”, undefined, …punch stuff…, “c”, undefined, undefined, “z”, undefined…] Want an array with just stuff without undefined how to actually do that in most optimized way? I thought not being in this situation is the best thing but hey what’s the next best thing then
I tried to learn javascript after languages like c#, c++. It just doesn't make sense. It makes! But when I found out TypeScript it became so much better.
Js is so flexible that even their developers haven't yet discover the limit. Webs, apps, games, data storage, backend, soon AI can be programmed with Js.
You're not wrong, but you have to admit, JavaScript's limits are being stretched. It has the potential to be a very volatile language, like Python, but it was specifically designed on the fly to handle and create behaviour on webpages. It wasn't designed to work on embedded systems, desktop apps, A.I or gaming. The way JS is able to enter into all these other fields of application is with alot of environments, libraries, frameworks and API's being engineered which allow it to be able to work in those environments, but that means that these environments have to be moulded to accommodate JavaScript which obviously calls for limitations in what you're trying to accomplish. JS may become more and more volatile and flexible and might eventually veer towards applications for a general-purpose language, but I think it will be a very long time before it becomes that and even when it does, I don't think it will ever outcompete languages that were specifically designed for those purposes. JavaScript becomes complex and very abstract rather quickly and was designed to be the ideal language for the web. Taking JavaScript and applying it to other things doesn't mean it won't perform, it just won't perform nearly as well or be able to do as much as you'd like. It's like taking a dog, which can swim well, and forcing it to live in the ocean: just because it can swim, doesn't mean it should live in the ocean. Being a jack of all trades and a master of none may be better than being a master of one in most things, but not when it comes to programming a software engineering. There is always going to be a set of tools and an environment which is niched for specific applications. The more complex and robust you get, the more specialisation and precision matters as opposed to just being able to get the job done.
@@fernando9175 I wouldn't call it "serious". They're niched for their respective environments and usages, where some are specifically designed to work for a specific context where no other language can work there. That's all I meant.
What's weird about it is that changing a variable can remove elements from an array. It would be more logical to have a resize method. I wasn't sure if increasing the size of array after it was decreased would bring back the removed element or not.
You shouldnt be able to change the size of the array. It should be read only. You can add elements to it if you want be because its an arraylist really but manually changing the size of the array under the hood is just dumb
Why is Banana no longer included in the array after the length of array is increased to 5? Is it because it’s being compiled as length being 2 so banana is cut off > then length is 5 so add three blank item > then input new word at array.[3]?
It would be a catastroph if you get an item in an array when you allocate more memory for it. Just imagine having a loop that goes thru the length of your array, and it is in your pacemaker and suddenly you allocate more memory and gets some garbage data in the array, and stops your heart. When he sets the length to 2, you erase everything beyond index 2. But since JS lets you dynamicly allocate memory for arrays, when you increase to 5 you get 3 empty items which you should expect. If you know what hashtable is, that is how Arrays work in JS
@@sharanoth still could have been done through a method rather then modifying the length attribute. Also, this only allows you to return a subarray starting at index 0 (a prefix), so not very useful tbh
In C say you allocate memory for an array with 255 items. But the software can get up to 300 items, making the software crash. Javascript just dynamicly allocate more memory and nothing happens.
Because JS arrays aren't like arrays in C or C++. At their base level, they are but JS has a very high level of abstraction which takes care of alot of the things you'd have to do to work on or create arrays. Everything in JS is an object and has an object prototype for their specific type. Number has a prototype object, string has a prototype object and array has a prototype object called Array. Arrays have .length property which defines the length of the array. Because this is a property on an object, it can be mutated. When it is mutated, it "syncs" up with the properties in the array object, which are what we call elements in the array. The .length property is defined by the number of elements + 1. You can see how this is different to a lower level language like C wherein you have to explicitly allocate memory space for an array by defining the length of the array at declaration. You can also declare an array in JS similar to how you would in C, but again, the length property is mutable. You can change this behaviour so that .length is not mutable, but yeah. Hope that helped. Go check out JS array and Array prototype on MDN.
I think he is probably a good coder. He is also one if the persons behind the rust language. He co-founded mozilla, he made the brave browser to name a few things. He is also around in the comments on youtube sometimes. Brandon Eich is his name. Lex Fridman did a good interview with him also.
This is a certainly an unconventional feature, its there for backwards compatibility, but I never had any issues with it because in my many years of coding with js I never had a scenario where I needed to assign a value to .length If you want something actually weird, you should look at how js spec handles the regex with global flag. Its one of the worst pitfalls of working with regex on js.
@@umairiqbal5172 ah, you are not adding to the array. When you write ['ab'] next to an array (edit: the object that is the array that is), its the same as you try to access ab in an object. So you add an object called ab to the array object. but you have not added anything to the array. so that is how it should be. its the same thing as arr.ab = 2
@@AndrewTSqSo JavaScript arrays are essentially objects , so when you do something like arr[0] = 1 you are giving it a property of 0 with a value of 1 and since this property is an integer it increments the length property. So when we do ['ab'] or ['0'] or [0] we are doing the same thing that is assigning properties to the object but the difference is that when that property is integer it adds to the length. Since I’m fairly new to JavaScript coming from Java some of these things feel weird like how you can slap properties on an object any time.
@@umairiqbal5172 I might missunderstand you, but arr[0] = 1 puts the value 1 in the array arr at index 0. It does not make a new property called 0. In Javascript if you have an array with objects (like arr = [{a:1, b:2},{a:4,b:4}] and you want to get to b:2 in the first array, you can do it like arr[0].b, or you can do it like arr[0]['b'] to access 2 . the last way is great since you then can use a variable to access different named objectkeys. so if i do b = 'b', i can then do arr[0][b] and get the same answer as arr[0].b or arr[0]['b'] . Arrays are like linked lists or hasttable in javascript.
I personally can’t see a reason allocating space in an array in Javascript is remotely useful, so I understand why this can be weird. Being able to just set the length down an arbitrary amount is cool though. Definitely not the weirdest function Javascript has.
Lower level languages don't do this. JS is object orientated, thus you can dynamically mutate the size of an array with the .length property which is really just a property on the Array object. In a language like C, you can't do this. You'd have to define a new array with the new size and then copy the original array's values into that array.
Yes, that's correct because setting the length to 2 removed the third item which would be index 2. Thus if you try to acces index 2, it will return undefined because the third value, at index 2 doesn't exist anymore.
Should have demonstrated by it a bit larger so people can see where this can go terribly wrong lol. The comments denote a naïveté around why this is weird. That scares me for the future of web development lol.
how do you handle a situation where you need more places in your array than you allocated then? Just let the software crash? JS makes this which is great.
@@michawielgus9827 and.. what do these languages do when you call those functions? It allocates memory and sets the pointer to new location. Just like JS does. An array in js can be a fast array or slow array. The slow array is more of a linked list. If people understood this then this .length makes sense
@@michawielgus9827 I have never seen anyone adjust the array by writing to the.length property so its a no problem. In modern javascript you dont need to use array.length. only people watching tutorials from 2015 does that
That's what it's supposed to do, isn't it?
No, its not. The length property shouldn't work that way, it should be a read property, never a write property. Any other type of behavior on this property, which alters its content, is a language malfunction and should be corrected in the future. There are too many cases like this that have not been fixed because too many programmers have gotten used to these bad practices, and as a result we have an inconsistent language with countless bugs, exceptions, and inconsistent behaviors.
@@Meister256 most bad practices kept in language for backward compatibility, so new versions dont break older
@@ky3ow of course, that is why there are migration processes from obsolete to current functionalities. Every language goes through that process and that's why there are different versions.
@@Meister256 " it should be a read property, never a write property" says who?
.
That's purely logical
no is not logical at all, it violate encapsulation principle and make a indesirable or not intentional side effect on state of the instance.
I mean the effects make sense, and could even be useful, however you should not be able to change the value of arr.length. It should obviously be read only.
@@poopfartlord9695Its probably unlogical for people used to say C where it works different. But in JS a array is not really the same thing as an array in C. one position in the array in Javascript takes up like tenths of bytes of memory. Already there we should understand that its not a normal array. Index 0 and Index 1 does not need to be saved next to eachother in Javascript memory. Its more of a linked list / hashtable behind the scenes. Thats why you can do things like this. I think its brilliant, and I dont care if some old law from 70ies programming think its wrong :)
Length should be immutable
@@rahff99 an array is just an object where the keys are the indexes and the values are the items...
so the length is just a getter/setter
Weird? It's the most logical thing js has lmao
Not many languages let you fuck around with an arrays length after initialization
@@camiscooked probably not but certainly not like that lol, there's some ways to extend an array but not fuck it up with the length attribute
Bruh true
Fax
lmao bro coded in js so much his programming standards turned undefined
This glitch shows we are living in the matrix 😊
That's not weird. What's weird would be setting the length to 5, then the program adds 'pear' and 'strawberry' to the array.
lmao😂😂
this is actually a very good feature helping manage array length dynamic
Meanwhile push and pop methods: ☠️
C/C++ developers having a stroke rn. 🤣
yup
Why?
@@kumarraj197 We are actually too much used to the restrictions provided in C/C++. There's too much leniency in datatypes or array length in Javascript.
not C++. we have a vector with similar behavior.
Imagine that they turned .length into a read-only and every single js framework dont work anymore
Lmao
the empty items are just properties on the array that dont even exist, thats why theyre not undefined but return undefined when you index them
just like an object key
I never faced the use case where I had to set an array's length and fill it with empty values.
Usually length is a trivial value that reflects how many items are left.
Ugh, I just found out recently you can assign values to negative indices and JS is just like, “sure thing, buddy 👍”
Lmao no way, js is really it's on thing
Here's a secret. Javascript doesn't actually have arrays. They're just objects pretending to be arrays.
its because arrays are objects duh
have you tried assigning string keys to arrays?
Imposter
@@electricengine8407yeah but ….
Whats weird? Was expecting something unlogical, but this was incredibly easy to understand
its like CHAR, the length is fixed but if you doesnt use all spaces in the array, they will show empty fields but with memory allocated
Turns out, this is a documented and supported feature. Wow.
JS never fails to surprise lol
Didn’t know that length is mutable 😮
In the grim dark of the 3rd millennium, there is only javascript
This isn’t weird, but it’s something I’ve never thought of. I will keep this in mind. I’ve been coding in js for 4 years lol
If you give static array number it does allocate the memory but doesnt put any value in there
Under the hood the array has to reserve memory. You can either reallocate the memory at ever add OR right aways allocate memory for e.g. 10 elements and then simply set them, which is supposing to be faster. The problem with script "kiddies" is: they never learn how this is ACTUALLY being implemented under the hood. If you learn programming in C or PASCAL you would understand that a collection either needs to dynamically allocate and move memory or use something like linked lists. Linked lists don't require reallocation but are SLOW. Continuous memory (array) is very fast but if you if you want an element that will require to grow the allocated memory this is costly. So typically a strategy to implement this to allocate more memory right away to avoid reallocation. In C#: arrays are fixed size. List has an option to specify a capacity but the size is dynamic (and internally a list is implemented as an array).
How does this really explain why some items are undefined instead of adding to the last possible item location or simply length is read property and there’s another write property like all other languages almost ??
Thus being said if I have an array of undefined how to get rid of all the undefined in an efficient way ?
Let’s say I have
[ “a”, undefined, …punch stuff…, “c”, undefined, undefined, “z”, undefined…]
Want an array with just stuff without undefined how to actually do that in most optimized way? I thought not being in this situation is the best thing but hey what’s the next best thing then
Now that's what I call, amazing 🤩
I tried to learn javascript after languages like c#, c++. It just doesn't make sense. It makes! But when I found out TypeScript it became so much better.
heya, can you share the name of the extension you're using to run the conde in the VS-code console? thanks
holey arrays have insane performance drops tho.
This video is beautiful. I enjoyed watching it.
Thanks
Isn't this super nice to set a constant array length?
That's the most sane thing in javascript
that's because length is a setter function
Js is so flexible that even their developers haven't yet discover the limit.
Webs, apps, games, data storage, backend, soon AI can be programmed with Js.
You're not wrong, but you have to admit, JavaScript's limits are being stretched. It has the potential to be a very volatile language, like Python, but it was specifically designed on the fly to handle and create behaviour on webpages.
It wasn't designed to work on embedded systems, desktop apps, A.I or gaming.
The way JS is able to enter into all these other fields of application is with alot of environments, libraries, frameworks and API's being engineered which allow it to be able to work in those environments, but that means that these environments have to be moulded to accommodate JavaScript which obviously calls for limitations in what you're trying to accomplish.
JS may become more and more volatile and flexible and might eventually veer towards applications for a general-purpose language, but I think it will be a very long time before it becomes that and even when it does, I don't think it will ever outcompete languages that were specifically designed for those purposes. JavaScript becomes complex and very abstract rather quickly and was designed to be the ideal language for the web.
Taking JavaScript and applying it to other things doesn't mean it won't perform, it just won't perform nearly as well or be able to do as much as you'd like. It's like taking a dog, which can swim well, and forcing it to live in the ocean: just because it can swim, doesn't mean it should live in the ocean.
Being a jack of all trades and a master of none may be better than being a master of one in most things, but not when it comes to programming a software engineering. There is always going to be a set of tools and an environment which is niched for specific applications. The more complex and robust you get, the more specialisation and precision matters as opposed to just being able to get the job done.
@@julianmcmillan2867 you are right sir.
And yes.
Java, Python, C++, Scala will always be the dominant for serious programing.
@@fernando9175 I wouldn't call it "serious". They're niched for their respective environments and usages, where some are specifically designed to work for a specific context where no other language can work there. That's all I meant.
What's weird about it is that changing a variable can remove elements from an array. It would be more logical to have a resize method. I wasn't sure if increasing the size of array after it was decreased would bring back the removed element or not.
What's the purpose of setting the length to a greater number if the output remains the same as it the elements were undefined?
Javascript is a people pleaser until "use strict"
That's expected behaviour
You shouldnt be able to change the size of the array. It should be read only. You can add elements to it if you want be because its an arraylist really but manually changing the size of the array under the hood is just dumb
It really said: "❤️ empty items>"
I didn't know this feature. I find it very cool.
I didn't ever think I can mutate Array.length value.
Why is Banana no longer included in the array after the length of array is increased to 5? Is it because it’s being compiled as length being 2 so banana is cut off > then length is 5 so add three blank item > then input new word at array.[3]?
It would be a catastroph if you get an item in an array when you allocate more memory for it. Just imagine having a loop that goes thru the length of your array, and it is in your pacemaker and suddenly you allocate more memory and gets some garbage data in the array, and stops your heart. When he sets the length to 2, you erase everything beyond index 2. But since JS lets you dynamicly allocate memory for arrays, when you increase to 5 you get 3 empty items which you should expect. If you know what hashtable is, that is how Arrays work in JS
just can’t imagine a use case to mutate the length so maybe it shouldn’t accept it
Performant way to return a subarray
@@sharanoth still could have been done through a method rather then modifying the length attribute. Also, this only allows you to return a subarray starting at index 0 (a prefix), so not very useful tbh
In C say you allocate memory for an array with 255 items. But the software can get up to 300 items, making the software crash. Javascript just dynamicly allocate more memory and nothing happens.
So if you specify a length , you can't overrun? It dismisses extra input? How?
Because JS arrays aren't like arrays in C or C++. At their base level, they are but JS has a very high level of abstraction which takes care of alot of the things you'd have to do to work on or create arrays. Everything in JS is an object and has an object prototype for their specific type. Number has a prototype object, string has a prototype object and array has a prototype object called Array. Arrays have .length property which defines the length of the array. Because this is a property on an object, it can be mutated. When it is mutated, it "syncs" up with the properties in the array object, which are what we call elements in the array. The .length property is defined by the number of elements + 1. You can see how this is different to a lower level language like C wherein you have to explicitly allocate memory space for an array by defining the length of the array at declaration.
You can also declare an array in JS similar to how you would in C, but again, the length property is mutable. You can change this behaviour so that .length is not mutable, but yeah. Hope that helped. Go check out JS array and Array prototype on MDN.
Whole JS is weird! I started learning it after learn Python quite well, and it was funny to me how much illogic there is in this language
Ive programmes a lot of different languages since 80ies and python is one of those. Why? Wierd syntax slow as hell
That was surprisingly normal behaviour for JS
Not weird at all.
It’s almost like the developers of JavaScript didn’t know much about programming
98% of webs are powered by Javascript but yeah they don’t know what they are doing.
It's almost like Javascript was designed by one guy in only 10 days
@@0x5D both can be true simultaneously
I think he is probably a good coder. He is also one if the persons behind the rust language. He co-founded mozilla, he made the brave browser to name a few things. He is also around in the comments on youtube sometimes. Brandon Eich is his name. Lex Fridman did a good interview with him also.
that is why you should go with typescript
That seems like intended behaviour, and pretty sensical behaviour at that
Love it when people don't understand something they say it is weird or magical (like Ruby on rails) 😂
How is it weird though ?
That's how arrays are supposed to work, not weird at all.
That's certainly quite a behavior
JS is the only language I use, so for me it's how it should work and I would find it weird if it did otherwise.
What's weirder is the amount of people saying this isn't weird
this is exactly what a non programmer would intuitively expect.
surprise surprise object oriented language has objects instead of actual arrays
Wow it doesn’t throw errors amazing
That’s the behavior I would expect tbh.
This is a certainly an unconventional feature, its there for backwards compatibility, but I never had any issues with it because in my many years of coding with js I never had a scenario where I needed to assign a value to .length
If you want something actually weird, you should look at how js spec handles the regex with global flag. Its one of the worst pitfalls of working with regex on js.
What about dates
Most logical thing in javascript :
should i delete the last item with this arr.length = arr.length -1?
JavaScript has a lot of weird magic, but this is not one of them.
Ever written in C?
Weird? It seems like it was beautifully designed to me.
'banana' still existing and had accessed the backroom
It's all object and an object is emulated as arrays so that's why except primitive everything in js is object
How about using const and not let?
Doesn’t matter. Don’t confuse yourself with reassignment and mutation.
Example: const arr = [1,2,3]
arr = true;
@@rockfox5 I know in this particular video it doesn’t matter. However it’s best practice to use const when possible, like in this video example.
I think it actually makes sense
The fact that it's purely logical makes it weird. JS is the weirdest shit I've been into
it mean you arent that much logical irl
What exactly was the weird part now?
You can set item to 6th item when your item length is 3. Your array length will be 7 then😊
Isn't this language great?
Now what’s weird is when you add non-integer key(index) value pairs it doesn’t contribute to the length of the arr.
how do you mean? it adds upp for me
@@AndrewTSq try const arr = []
arr['ab'] = 2
console.log(arr.length)
it should print 0
@@umairiqbal5172 ah, you are not adding to the array. When you write ['ab'] next to an array (edit: the object that is the array that is), its the same as you try to access ab in an object. So you add an object called ab to the array object. but you have not added anything to the array. so that is how it should be. its the same thing as arr.ab = 2
@@AndrewTSqSo JavaScript arrays are essentially objects , so when you do something like arr[0] = 1 you are giving it a property of 0 with a value of 1 and since this property is an integer it increments the length property. So when we do ['ab'] or ['0'] or [0] we are doing the same thing that is assigning properties to the object but the difference is that when that property is integer it adds to the length. Since I’m fairly new to JavaScript coming from Java some of these things feel weird like how you can slap properties on an object any time.
@@umairiqbal5172 I might missunderstand you, but arr[0] = 1 puts the value 1 in the array arr at index 0. It does not make a new property called 0. In Javascript if you have an array with objects (like arr = [{a:1, b:2},{a:4,b:4}] and you want to get to b:2 in the first array, you can do it like arr[0].b, or you can do it like arr[0]['b'] to access 2 . the last way is great since you then can use a variable to access different named objectkeys. so if i do b = 'b', i can then do arr[0][b] and get the same answer as arr[0].b or arr[0]['b'] . Arrays are like linked lists or hasttable in javascript.
I personally can’t see a reason allocating space in an array in Javascript is remotely useful, so I understand why this can be weird. Being able to just set the length down an arbitrary amount is cool though. Definitely not the weirdest function Javascript has.
I don't think typescript will let you play with this xD
So students a array cannot change its size..
JS : What? I didn't hear you!
Whoever is saying this is logical... Length cuts data??? Also Which item should push function act on 6, 5 or 4?
Js wasn't strange enough, they need to add this
Tell me you you have never managed raw memory without telling me you have never managed raw memory
It's not only array length that is weird in JS.
The item exist and its value is undefined
More of this please!!
Which theme you are using?
There are a lot of weird things in our world, son
and how it’s wired? Looks absolutely logical.
so setting the length to 2 actually removed banana?
If you think arrays as memory positions this behavior is very logic.
Java Scripts seems to be a mix between C++ and Python.
That's because everything is object in javascript
JavaScript arrays>>
People saying its normal or some shit has only coded in JS. It's not normal to be able to do this in any other language.
Im so confused how length is a mutuable property
Still trying to find what's weird about all that
Lower level languages don't do this. JS is object orientated, thus you can dynamically mutate the size of an array with the .length property which is really just a property on the Array object. In a language like C, you can't do this. You'd have to define a new array with the new size and then copy the original array's values into that array.
oh wait I see something here, js actually write it this way for non-computer person to define.
In js world everything is an object even undefined and that's why I hated it
You should define arrays with const. That's actually more weird.
arr[2] = undefined? Index is start at 0 while length starts at 1 in counting. Im not sure.
Yes, that's correct because setting the length to 2 removed the third item which would be index 2. Thus if you try to acces index 2, it will return undefined because the third value, at index 2 doesn't exist anymore.
peekaboo is weird. when i move my hands from my face, my face is visible again.
This is common in compiled languages
What if you make th le default length of an array to 5?
That's how dynamic arrays work bro 🤌
Should have demonstrated by it a bit larger so people can see where this can go terribly wrong lol. The comments denote a naïveté around why this is weird. That scares me for the future of web development lol.
You just need to learn how to use the tool before using it to avoid common mistakes
Length should be designed as a function method, so it can't be modified .
how do you handle a situation where you need more places in your array than you allocated then? Just let the software crash? JS makes this which is great.
@@AndrewTSq provide a method allowing you to add additional elements? Like .append in python or .add in java
@@michawielgus9827 and.. what do these languages do when you call those functions? It allocates memory and sets the pointer to new location. Just like JS does. An array in js can be a fast array or slow array. The slow array is more of a linked list. If people understood this then this .length makes sense
@@AndrewTSq than make it implicit and not some whacky shenanigans. No other language does it this way
@@michawielgus9827 I have never seen anyone adjust the array by writing to the.length property so its a no problem. In modern javascript you dont need to use array.length. only people watching tutorials from 2015 does that
This smells like a leaky abstraction.
Also, you were getting length property, not calling. That is a two very different things.
How is this weird? I'm not even that good at programming and this is how I would expect it to work...