ExFAANG Engineer Watches ExFAANG Take JavaScript Quiz | Prime Reacts
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- Опубликовано: 7 фев 2025
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Reviewed video: • ex-FAANG Developer vs ...
By: / @connerardman
/ theprimeagen
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I love that I have pretty much 0 experience with JS, and yet I can get every single question right by asking myself “what would be the craziest possible result here?”
Yeah they should've thrown some normal curve ball questions, so people don't automatically default to answer with the craziest possible choices.
Except they did.. there were some normal expected ones there.@@kiattim2100
Just like in high-school, hahha...
they were just overcomplicating them. For most of them I could just look at it and be like yeah, 0 is false is true. duh.
You ain't fooling me
“I am currently a FAANG developer at this moment” - this was foreshadowing
severely underrated comment
what happened where does he work now
javascript feels like when i try to interpret my dreams
And it works, but in mysterious ways.
Javascript was a mistake.
This joke made me crack a rib.
Profile picture checks out.
😂😂😂
The interview: "Invalid octal 018 that defaults to decimal minus valid octal 015"
The job: "Should I try to add this through more polymorphism or slap a Visitor pattern into all these classes?"
Uncaught SyntaxError: Octal literals are not allowed in strict mode.
@@fredoverflow hello this is CORS and fuck your app and especially those octal craps, I don't like them
perfect profile pic for this comment btw
When you can go Visitor, always go Visitor
roll your own rtti
For the Raw string question, in Python, we often use raw strings to type regex. They are already complicated enough, and we don't want to make them even more complicated by having to escape all the backslashes
It's also much nicer in Python because you just have to prepend an 'r' and you're good
And in Python you have to prepend 'f' to get variable formatting inside the string. (which you can combine with 'r' to get that French strings 🥖)
*python2 flashbacks*
Sounds like a skill issue. Real programmers escape all the backslashes and charge their employers for the time spent doing it. ;)
Same main reason why String.raw was introduced in JS; to be used to create regex patterns as strings that can be compiled to RegEx objects later that can be processed. Before this you'd have to escape the escapes, e.g. /Hello
World/ into `Hello\
\
World`.
It is truly amazing how much of JavaScript you miss out on by not doing aggressively stupid things with it
100% this
I just gave this comment its 70th like. Sorry about that.
@@RichardRemer The largest problem is the same issue I have with PHP not running in strict mode. Even if I'm coding in TypeScript, at runtime an API could return the wrong type! It's a philosophy decision. JavaScript and PHP are deliberately designed to continue execution with garbage data rather than fail.
If your code does not look like
var myInt = new Array(0b17 % spaghetti*4);
... you are not really coding
Yeah I hated every second of this
Can’t tell if I’m being gaslit or if I have been saying NaN wrong all this time…. 😅
I mean, there are multiple ways of saying it.
“Nan”, “N A N” or “Not a number”.
Just like SQL.
“S Q L” or “Sequel”.
@@Greedsmith "Squeel"
say it how u feel
I finally understand the rust people.
Its javascipt devs who got out of a toxic relationship and now they want to date the opposite person.
The borrow checker might be annoying, but have you ever programmed in Javascript? - Rust devs
And after dating their opposite, theyll balance out in the middle, Go.
Or they take another detour and go elixir for a year
It's more like they have pathological tendencies and can't avoid toxic relationships, they went from idealizing JS to idealizing Rust.
Nah most of them go TS. Once they dip into the crazy they're hooked for life.
Funnily enough, I really like both JavaScript and Rust.
They complete each other.
In a javascript quiz the answer is always "why"
I find that applies more to languages like rust where everything is “ugh” and “why” and “do I really have to do all this and write macros for something that would be 1 line in c# or js”.
(Sorry, just learning rust and not having a great time. JavaScript looks pretty nice right now)
quiz is the answer. why is the question
@@svenmify rust is comparatively low level than c# or js. That's why.
@@testacals oh I know that. But something like Swift is also lower level (arguably a little less than rust), but way easier to code in.
A lot of the stuff I dislike about rust are design decisions
@@svenmify
Looks like Harrison Ford recruited yet another aspiring rust cul... developer.
Alternative title: "When you create a language over a weekend"
10 days actually
@@fredoverflow 🤓
Hey man, just wanted to thank you.
I'm learning to code and despite working in tech for over a decade, there's a part of me that has always resisted/dreaded coding because in my mind it has always seemed like the epitome of postmodern desk slavery.
But you make it fun. You're always super hyped and having fun with coding. I'm not really learning that much from you, but listening to you having so much fun with it just makes it seem less soul sucking and has helped me have more positive associations with coding, which has really motivated me to do more learning in my spare time.
Just a fellow anon or here appreciating your passion. Never change!
This is really interesting to me.
Since in my mind code was always the thing that lets me make the computer do things.
Like, it's the stuff that video games are made out of and the fact that I know how to do that now would probably make 5 year old me happy. (and also makes me happy now :) )
@@cameron7374 yeah I'm coming to see it more like this now, largely thanks to prime and LLL.
It's weird - I had his experience with manufacturing first. When I started working with startups and got to see how things are made behind the scenes, actually going to suppliers, operating high tech machinery, working with vacuum chambers and plasma and lasers and CNC machines etc, it gave me a massive appreciation for the whole process. I was instantly hooked.
But software always seemed like the drab side of things. Working with hardware was interesting and seemed like it had more room for creativity; coding just seemed laborious, just stitching together the hardware with boring 1s and 0s.
It took actually taking a coding class and building some CLI apps in C to give me that same feeling about code. I see now how much of a rush it can be to problem solve with code, how intellectually stimulating it can be, and above all else how rewarding it is to build something that really works.
I'm taking a break from studying at the moment because my daughter was just born a few months ago, but watching prime and keeping up my practice on sololearn has me excited to get back to my comp eng classes.
I am pretty sure the title changed from “FAANG engineer reacts to ExFAANG engineer” right after the announcement on the main channel lol
lol he updated the title cause he left Netflix 😂
I don't know about Javascript, but in other languages, the main use cases I've seen for raw strings are:
1. Writing regexes without having to escape \
2. Pasting the contents of a multi-line text file into a string literal.
3. Writing GLSL shaders or other dynamically compiled code from a different language, so they don't need to be shipped as separate files.
4. Writing multi-line strings for whatever other reason.
I love this one even more:
String('123') instanceof String
JS is truly a language of all time
Pure rage.... But also, you construct new String objects with `new String()` and the fact that it doesn't crash when you do that without new is the part that's actually weird and wrong
@@itsteelworksof course. String is a function that converts things to primitive strings, and new String is a constructor that creates String instances.
You can even do this with your own types, just check new.target in your functions or constructors and return a value to use instead! Just remember that you can't return a primitive if the caller used new, or it will ignore the value and return the this value it created for you.
It's so simple and nice! 🫠
But Object('123') instanceof String is true
same for new Object()
Javascript, I love it
@@RichardRemer But why would a cast using String result in a string, I would not call that "consistent" at all. The sane expectation still would be that it casts to String, not string.
I love that after 20min of bamboozling there was a phrase in an explanation to one of the questions: “if you do this instead you’d get a result you would have expected from the beginning”. You can’t expect anything after that
Q1. Octal number literals without prefixes are a syntax error in strict mode, and any code written over the last 15 years has no reason to not be written for strict mode.
Q4. I would never rely on the == algorithm which is recursively defined with 15 branches, a real nightmare. Still, in this case, given two primitives where one is a boolean, it casts the boolean to a number. Then given a number and a string, it casts the string to a number. 0 == 0 is true.
The explanation given was wrong because it suggests that false is first coerced to "0", but it isn't. In fact, at 14:00 a correct explanation is given for another question. The == algorithm never converts other primitives to strings. It does convert objects to primitives before comparing them to primitives, which looks for a `Symbol.toPrimitive`, `valueOf` or `toString` method on the object in that order, and otherwise throws. Most objects inherit from Object.prototype which has a default implementation of `toString`, which is why you might think == falls back to strings, but the blame lies on the ToPrimitive algorithm for objects only.
But wait, I've seen people write `if (value == null)` to check for both null and undefined, would that throw if given an object that doesn't inherit from Object.prototype? No, because the == operator is explicitly defined to perform comparison to null or undefined early, so it won't even attempt to cast an Object when comparing to either of them. Yes, == is horrible, if JS didn't have to stay backwards compatible it would have been replaced instead of === being added.
Q6. As you explained, this creates an array with empty items, or holes. The explanation provided on the quizz actually gets that right... only to then represent that as [1, 2, 3, undefined, undefined, undefined, 9] which is not correct. The proper array literal representation would be [1, 2, 3, , , , 9] but as you showed, dev tools are nice enough to tell you the number of empty items instead.
What's the difference between a hole and a property? A hole doesn't block inherited properties. So Object.setPrototypeOf([1, 2, 3, , , , 9], [,,,4,5,6]).map(x => x) produces [1, 2, 3, 4, 5, 6, 9]. And because of this, accessing elements on an array with holes is incredibly slow.
Q7. The explanation here is correct, but what ThePrimeTime says isn't. We say a value is truthy if the ToBoolean algorithm would return true, not when it is == true. Arrays are objects, objects are truthy, so even empty arrays are truthy. The reason false == [ ] is true is once again because the == operator uses the ToPrimitive algorithm which, on objects can end up calling toString.
false == [ ]
false == ToPrimitive([ ])
false == [ ].toString()
false == ""
ToNumber(false) == ""
0 == ""
0 == ToNumber("")
0 == 0
true
Again, this is never a problem in the real world because you do not use == in the real world.
Q9. Including the quotation marks is inconsistent with previous questions and confusing. String.raw`HelloTwitter
world` is equivalent to the string literal "HelloTwitter\
world" but your console would likely log HelloTwitter
world without quotes and without escaping the backslash.
The point of String.raw is for when you want to write some code inside a string, and don't want to have to escape the backslash twice if the language of the code you are writing also uses them. It's similar to the r prefix in Python.
Q10. Not an issue with the question, but I did use new String once to experiment with WeakMap, whose keys have to be objects. I've yet to find a convincing use case for WeakMap though.
It cares more about debugging and foundational understanding than pure DS&A.
I have to admit, against my better judgment, I like this quiz.
If you grew up with a typewriter (before eg graduating to a Vic20), the newline+return sequence makes perfect sense as they were two very distinct actions. 😂
Greatly enjoyed this episode.
Gotta send the printer back to the left side of the page after new line.
Super fun yea
I think the odd keyboard still has an enter/return key with an arrow on it that goes downwards and then points back to the left. The clue to 13 and 10 being two instructions hence two characters is even there.👍 But you're right. If you've used a typewriter before you can't fail to differentiate line feed from carriage return.
I wonder... Should the 'return' key be called the line feed carriage return key for completeness? 🥴😂
I'll have to lay down after this
I love that you would never actually run into these problems if you code properly
Jr devs to the rescue!
JS's type coercion is a crime against humanity. Most of these questions should just TypeError…
"If it's true, I'm gonna commit sudoku". Wow that's some high level of devotion to the cause man! :D
HE CHANGED THE TITLE OMG
lmao, that was a short-lived title.
this is so good.. Please do more of this.. Your channel is crazy awesome
now it's an ex-faang developer watches ex-faang developer take javascript quiz
I like how Prime says "ha ha, look at chat in disbelief" and continues to be in disbelief for the next question himself 😔
Hearing expert JavaScript developers talk about its type system is a prime example of Stockholm Syndrome.
""""" type system """""
It's kinda entertaining to see chat slowly become completely hysterical, ngl.
@14:15
theprimeagen: *concentrating very hard to follow the exact logic behind Javascript's blackmagik type conversion*
chat: uh-huh-huhhuh...he said "bang array"
😂
In the future fang engineers will be the people designing cyborg vampire teeth
From the ECMAScript spec:
7.2.14 IsLooselyEqual ( x, y )
The abstract operation IsLooselyEqual takes arguments x (an ECMAScript language value) and y (an ECMAScript language value) and returns either a normal completion containing a Boolean or a throw completion. It provides the semantics for the == operator. It performs the following steps when called:
1. If Type(x) is Type(y), then
a. Return IsStrictlyEqual(x, y).
2. If x is null and y is undefined, return true.
3. If x is undefined and y is null, return true.
4. NOTE: This step is replaced in section B.3.6.2.
5. If x is a Number and y is a String, return ! IsLooselyEqual(x, ! ToNumber(y)).
6. If x is a String and y is a Number, return ! IsLooselyEqual(! ToNumber(x), y).
7. If x is a BigInt and y is a String, then
a. Let n be StringToBigInt(y).
b. If n is undefined, return false.
c. Return ! IsLooselyEqual(x, n).
8. If x is a String and y is a BigInt, return ! IsLooselyEqual(y, x).
9. If x is a Boolean, return ! IsLooselyEqual(! ToNumber(x), y).
10. If y is a Boolean, return ! IsLooselyEqual(x, ! ToNumber(y)).
11. If x is either a String, a Number, a BigInt, or a Symbol and y is an Object, return ! IsLooselyEqual(x, ? ToPrimitive(y)).
12. If x is an Object and y is either a String, a Number, a BigInt, or a Symbol, return ! IsLooselyEqual(? ToPrimitive(x), y).
13. If x is a BigInt and y is a Number, or if x is a Number and y is a BigInt, then
a. If x is not finite or y is not finite, return false.
b. If ℝ(x) = ℝ(y), return true; otherwise return false.
14. Return false.
ℝ(x) stands for the mathematical value of x, which normalizes +0 and -0 into 0 and is not defined for non finite values.
4. NOTE: This step is replaced in section B.3.6.2.
EXCUSE ME?
The best part is JavaScript added “use strict” and none of these are addressed by this flag, you would think that octals would have required the 0o syntax. Maybe they should add a “really use strict” flag!?
"For real this time"
May I introduce you to Perl's pragmas :P
Both 015 and 018 do throw errors in "strict mode" though?
@@fredoverflow You’re right, but how many people use “use strict” because of the limited improvements that come with it? I tried using “use strict” in REPL mode (both console and Node) and that doesn’t work, I should have written it in a file to test.
It should have made coercion apply to only one side of the comparison and only be applied once, arrays should have required to be the same type for all elements, and add boxing of values. With the number of people who create videos like this, it shows that removing these problematic behaviors would lead to less errors for developers.
@@RichardRemer My problem with “use strict” is that it doesn’t apply enough changes to fix these tricky questions in the quiz. One of the biggest issues is inconsistency with type coercion, when sorting it always casts to string but then in comparisons it doesn’t and it can cast more than once. There needs to be a stricter set of rules that makes type coercion only work for comparisons and arrays are only allowed one type, this would fix the majority of the problems and have types that are predictable.
~26:40 - The rule is not completely consistent, at least not at first glance. Java uses a String pool for optimization and Strings that are referenced multiple times are therefore the same instance and `==` returns true. However that is not the case for all methods that can create new Strings. I do not know which methods create separate instances and which do not
It also differs based on JVM implementations, such as OpenJ9 having stricter string interning. You should definitely always use `.equals` when comparing strings, it short-circuit checks refs in the equals implementation anyway!
I'm going thru like a worst phase of my life! Both professionally ans personally.
Watching your videos makes my day. Thanks Prime.
24:26 YES, I have used the String constructor for an actual functioning purpose.
When you use the strings as map keys and two of those keys might be identical strings BUT you want to process the identical strings differently (for instance, based on their position or based on a user-selected process), then if you map the strings to their processing outputs, using String constructors lets you map two identical strings to two different processing outputs. If you didn't use the constructor, the second string processed would overwrite the first when you map that process output to the string, which you don't want if your goal is to process the two strings differently.
The catch is that you have to handle all keys symbolically or retrieve them with a keys() function call if you want them, which is fine since you're probably going to be processing dynamic instead of literal strings anyway.
Now, here's a bonus JavaScript quirk in the form of a quiz problem:
let a = new String('hey');
let b = new String('hey');
let c = 'hey';
console.log(a == c); // guess the output of this first, then try it
console.log(b == c); // guess the output of this second, then try it
console.log(a == b); // guess the output of this third, then try it
I actually got wrecked by sort implicitly casting to string once. Worst part was that I wasn't actually the one writing the frontend I wrote the backend that consumed the sorted array.
tbf if you expect a sorted array and the client does not send a sorted array, that's an FE issue not a BE issue.
But also there probably shouldn't be the need for a sorted array and the BE should sort the array itself regardless
@@xelspeththis. Everything should be done in the backend except fetch requests, storing cookies/temporary identifier variables, and DOM manip unless you have a specific edge case (such as using WASM or somehow not having a backend for your calculator website). If your company doesn't have control over the full tech stack though, then you're gonna have to contact the frontend devs to redesign your protocols for what data to send over the wire.
Besides regex, raw strings can also be for windows paths.
I love the title change. 😄
Very interesting video, I got almost all of them wrong, except for the String.raw
I've had to use String.raw before when parsing JSON where some of the object attributes are also JSON (doubly stringified!), to avoid the backslashes in the double stringified json being used as escape characters
This is why I love the ThePrimagen: he turned an 11 minutes video into a 30 minute reaction. He's not just sitting there in the corner; he actually adds to the content. Love it.
Mdn doc on '==' say It works ona case by case basis so:
> Number to String: convert the string to a number...
So the explanation by the quiz was correct.
2:10 I just learned that NaN is "Not a Number"... after all these years
Javascript makes C's undefined behaviour look sane
21:50 In the case that you're saying you don't know how to use it because you don't understand it, since it's raw but not really because it still evaluates the variables, the best way I can explain it is that that's only due to the backticks (``) surrounding the text, which I assume tells Javascript to evaluate the variables, and String.raw doesn't really interfere with this process. If it had the single or double quotes, it would have included the ${varOne} and ${varTwo}.
And in the other case where you are wondering why you would need to use String.raw at all, I have found myself needing to use this at times when I was trying to either be able to log out the raw thing in LLM responses, since I was trying to figure out if it was giving
or
alone. I bet there's some dynamic finetuning data generation use cases too.
I am unreasonably perturbed by the fact that `[]` can be coerced into both `true` and `0` depending on the type chosen.
It felt good to get one of those questions right, i was air humping the raw dog question
Oh god how do I delete this comment
DONT DELETE IT
@@ThePrimeTimeagen 😂
now it will have to be an ExFAANG
Need to update the title as there are two ex-FAANG-ers here now))
21:55 logging, debugging... when you want to see what's in the string. If whitespace gets printed regularly, it's difficult to see which type of whitespace it is.
Not calling it String.rawdog is a mistake and you can't change my mind.
Principle of most surprise lmao. Actually insane that js became so dominant.
"I am currently a FAANG developer... as of this moment"
Bro was telling us the writing on the wall.
JS is responsible for a whole generation of programmers thinking this sort of shit is acceptable and you can see it in their code.
I wish you would put the links to the materials you are reacting to in the description, that seems respectful but also helpful, this has bothered me several times is when I wanted to try to go look at it myself. Love the content though. I wish I had the video that I made you react to once which was dave portnoy the barstools sports founder ranting about bitcoin, comparing it to "that emoji game" and so on, it was taken down for some reason. by the way, you are wrong about the conversion, 1 == "1" converts those to numbers, hence e.g. 1 == "+1.0e0", edit: lol sorry this was explained just a few minutes later, I think the explanation is that it's kind of like a special case that strings when compared to numbers is done that way, and then false is simply always converted into zero, but yeah I can't explain it either. it doesn't really make any fucking sense whatsoever
i do almost always have it... if its not in there, then its a mistake more than anything else. total accident if there is no link
"5 empty items" becomes even more cursed because in some cases "empty items" from an array can end up in non-array objects with string keys, and then there is no way to remove them
Just curious, does anyone here actually write conditions that depend on Javascript's type coercion system? Personally I avoid it like the plague and just make the most explicit conditions possible whenever I'm nose plugging my way through a JS build.
Not anyone that has ever loved anyone in their life, I'm sure.
26:25 BTW, JAVA handles strings with a stringPool. Each unique string has one reference in memory, so comparing the reference or the actual value is the same. Unless you compare “a” == new String(“a”), then the reference is different.
But “a” == “a” is true
javascript is the definition of "just because you can doesn't mean you should"
In the question 4, 0 == '0', '0' is converted to a number.
The specs:
Abstract Equality Comparison (==)
The comparison `x == y,` where x and y are values, produces true or false. Such a comparison is performed as follows:
1. If `Type(x)` is the same as `Type(y)` then
1. 1. Return the result of performing Strict Equality comparison x === y.
2. If x is null and y is undefined, return true.
3. If x is undefined and y is null, return true.
4. If `Type(x)` is Number and `Type(y)` is String, return the result of comparison `x == ToNumber(y)`
5. If `Type(x)` is String and `Type(y)` is Number, return the result of comparison `ToNumber(x) == y`
6. If `Type(x)` is Boolean, return the result of the comparison `ToNumber(x) == y`
7. If `Type(y)` is Boolean, return the result of the comparison `x == ToNumber(y)`
8. If `Type(x)` is either String, Number or Symbol and `Type(y)` is Object, return the result of the comparison `x == ToPrimitive(y)`.
9. If `Type(x)` is Object and `Type(y)` is either String, Number or Symbol, return the result of the comparison `ToPrimitive(x) == y`.
10. Return false.
we had something similar as an exam in school. the results were literally that 25% of answers were correct. Which means the results of the entire class were the same that you would expect if everybody just answered randomly.
"I am currently a FAANG developer at this moment"
17:20 NaN2 would also make sense, number + string = 'NaN', 'NaN' + '2' = 'NaN2'
But this is one of the few where JS actually makes sense as it treats everything equally
At 6:50 ish -- As far as I can find, even though it's counter-intuitive, I believe it actually tries to convert the string argument to a number to do the comparison. If you try 5 == '5.00000' it returns true. If it was as simple as the number argument being converted into a string, these would not be loosely equal. Instead '5.00000' becomes 5
*Edit* : Should've watched further, didn't think he'd come back to it. Prime talks about it again around the 9 minute mark
8:42 It would've been fun if the question was baity and said. 0.2+0.3==0.5. _Although_ floating point can have inaccuracies, that's an example that works out.
String.raw can be used to get syntax highlighting for the code inside a string, for example, make a function named "yaml" and just return String.raw from it, call the function somewhere, write some yaml inside the backticks and you get yaml syntax highlighting, at least if you use neovim with treesitter.
The fun one with question 8 that I always catch in code reviews is someone wanting to shorthand a long hand for loop on an array as `for (const i in [1,2,3]) { }` and then for some reason in the code they have to do index manipulation and have no idea why shit isn't working, and it's because the keys going into i are strings and it's concatenating rather than adding.
every time I hit pause because I thought the in-video pause was on my end, I get back to work.
I cannot wait for the Javascript Apocalypse, when Raytheon starts programming nuclear weapons using Node.
Imagine explaining that to your mutant descendants.
Non-FAANG Engineer Watches FAANG Engineer watching ExFAANG Engineer take JavaScript Quiz
Apropos \f (also known as ^L or "form feed"): fun fact, GNU source code is partitioned with form feeds. I haven't see anyone else do that, but it's extremely common in GNU projects.
God! This is the best video I watch since the beginning of 2024
I get the vibe that he prewatched (or took this quiz already). Especially since he used the word “quirk” like in the explanation
When us electrical engineers work with Modbus RTU and other similar serial interfaces it is nice to make use of Node.js to script some code and work through a COM port. In that case the raw works nice
'A very confusing conversion system' is what you tell someone just starting to learn js to give them a heads up without spoiling how atrocious everything is.
Windows users know all about raw dogging strings C:\\señor
I understood most of these, and I can accept most of the ones I got wrong, but the fact that string literals are not instances of strings despite their prototype being string makes me incredibly angry.
you'd use the constructor String in a case where you have a defined array of objects holding type/value pairs (i.e. a configuration map) and you want to map over it in your runtime and create the variables.
here's a one liner: `const data=[{t:String,v:'my string'},{t:Number,v:12}];const instances = data.map(({t, v}) => new t(v));`
The floating point one got me because its obviously false in the general case, but there are numbers that reproduce perfectly in floating point so I assumed this was one of the special cases where the stars aligned and the equality held
omg the fact that I knew all of these even without multiple choice just shows how little hope is left for me in my javascript-rotted brain, lol
"new Array" in JS can take a long walk off a short pier
7:12 here's a way how to test it:
false == '00' // -> true
0 == '00' // -> true
String(0) == '00' // false
Edit: Aah, he came back to it at 9:10 with the same test as mine 😅
9:04 I incorrectly guessed it would be true, just because of the loose equivalence operator instead of a strict one. In my head I figured js would go the extra mile and either round to the same floating point placement or just chop off. But I was wrong lol
3:10 the exact same question was in my midterm a couple of days ago and my smartass for some reason thought that typeof would return a sort of Wrapper class so like actually Number not a string (Java reference)...but that turned out incorrect obviously...
I don't know who wants to know this info, but if you do
arr.map(_ => 99) while the arr = new Array(5) --> means empty array of five.
You can use fill before the map to turn all items to undefined then map through it.
arr.fill().map(_ => 99) will work.
Java will not duplicate strings in the heap when created with double quotes, so "foo" == "foo" will return true even though it is technically comparing references instead of values. You have to explicitly create additional objects with new String() to break the equality.
Why is there ever a moment when we would need loose comparison which can not be done by other more standard ways (seriously asking) ?
The raw string stuff is used when using regex in a language using strings. Everything needs to be backslashed to count in regex, so it need to stay and not "dissapear" as it would in a real string. I did it in python tho so I dont know about javascript, but I assume its the same
If JS was not trying so hard to not throw, it could have been so much better
Updated title: “ExFAANG Engineer Watches ExFAANG Take JavaScript Quiz”
The only reason to use a string constructor is if you've monkeypatched or extended String with additional methods, which you shouldnt do 99% of the time
One use case for String constructor is if you want to store other properties against the string (eg isTranslated)
let s = "hello";
s.isTranslated = true
console.log(s, s.isTranslated)
s = new String("hello")
s.isTranslated = true
console.log(s, s.isTranslated)
at 12:30 there are a few other ways to create empty items. one that comes to mind is [,,,,,,,,,]
7:10 "I don't know how to test it"
Well, you can compare: false == ' 0'; // added leading space
This will still be TRUE, and that's because both values are converted to Number. If they were converted and compared as strings, '0' wouldn't be equal to ' 0'
so the only time I've used a raw string was to identify different dating formats or directories with regex. but that was in python, idk if it would have the same application in JS
I suppose that JS victims may use raw strings to genererate dynamic code that includes a call that prints out a new line, for instance.
Being real, if you are in a situation where you need to consider those situations, your code is already f*ucked from at least 2 sprints ago 😂
the meme is becoming real:
reacting the reaction of the one who reacts 😂
i use js for all kinds of things, including scripting serial ports.
And i've used the string constructor to ensure proper type conversion in mozilla rhino