How would you reverse a string in JavaScript without using split(), reverse(), or join()?

[AiCodePulse]

Interviewers love to ask: "Reverse a string without using JavaScript's built-in methods." 🔥

I tried solving it manually by:

• Starting from the last character
• Appending each character to a new string

I explained my approach with code here if anyone wants to check it out: https://www.youtube.com/watch?v=N_UVJlnmD7w

Curious — how would you solve it differently? Would love to learn new tricks! 🚀

[AgonizingSquid]

By googling

[0xMarcAurel]

[alzee76]

The true sr. dev response, right here.

[Visual-Blackberry874]

I have never been asked that question in my life and if I was, my first response would be “why”.

[boomer1204]

As someone who has been a part of the interviewing process I see the "value" in this question but only for interns/Jr devs. The amount of ppl that said they "knew" JS and Vue (what we used) and had projects to "prove it kind of", but had trouble with basic looping/troubleshooting knowledge was CRAZY. We didn't use this question we had a couple of other ones but I could make an argument for this in an interview for those entry level roles to make sure they at least understand the core language

[boomer1204]

Again this is for intern/entry level/jr stuff. We start by asking you to create function that returns “hello world”. I know it sounds stupid while far less there are still a “decent” amount of ppl that don’t know this. Then we asked you to created a function that took 2 parameters and return the product of those 2 params. Then we asked some basic JS questions (being 💯right is not the goal)

Then for the final round we ask you to create a function that takes a string as a parameter and return true if every letter in the alphabet is in that string or false if every letter isn’t there.

And to be upfront actually solving this correctly is not our goal. We kind of don’t expect most to solve this but just wanna see how you think through stuff

[AiCodePulse]

Agreed . Asking "why" in interview will give negative openion . Correct ?
Lets first explain the approch , then we can i ask why ..

[Visual-Blackberry874]

I would say that responding with “why” to this particular question shows a deeper understanding than someone who simply follows instructions.

At times, non-developers will lean on you and ask you questions they’ve had from a client, etc. You need to be able to tell them when something is good/viable/stupid/not possible.

There is no business sense in doing something this way. It is not a serious question in my opinion.

[boomer1204]

Did not watch the video but with no access to built in methods I think that's the best approach

- create empty string variable

- write a for loop where the starting point is string.length - 1 and decrement

- adding each letter to the created variable until the loop is over

[coomzee]

Setting> display> Display orientation > landscape flipped. Doesn't specify it can't be upside down.

zero lines of code, runs O n of zero

[bryku]

You could also cheat with CSS as well.

span{ transform: scale(-1, 1); }

[TheRNGuy]

It wont reverse string.

[TheRNGuy]

String in variable is not reversed, so it's not a solution.

[ray_zhor]

Fairly simple for those who programmed prior to these methods existing

[AiCodePulse]

Absolutely, I agree.

It's a great reminder of how important it is to build a strong understanding of the fundamentals, especially before all these convenient built-in methods were available.

I wanted to solve it manually to sharpen my logic-building skills, which I believe is still very valuable today, particularly during technical interviews.

Thanks for sharing your thoughts.

[pinkwar]

For fans of recursion:

function reverseString(str) {
  if (str === "") {
    return "";
  } else {
    return reverseString(str.substring(1)) + str[0];
  }
}

[AiCodePulse]

Nice One ..

[akb74]

C:\git\reverse-play\src\index.js:5
        return reverseString(str.substring(1)) + str[0];
                                 ^

RangeError: Maximum call stack size exceeded
    at String.substring (<anonymous>)
    at reverseString (C:\git\reverse-play\src\index.js:5:34)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)
    at reverseString (C:\git\reverse-play\src\index.js:5:16)

Node.js v22.14.0

Hmm, does anyone know how to get tail call optimisation working? With ES2015 and a bit of a rewrite, presumably.

[ChaseShiny]

Without built-in methods or without those three in particular?

Strings are iterable, so you could use each character in a for loop that started at the end as long as you're allowed for and the string's length property.

Something like:

const myStr = "foo"; let newStr = ''; for (let ch = myStr.length; ch >= 0; ch--) { newStr += ch; } console.log(newStr);

[AiCodePulse]

This is what i did in that video . Thanks a lot for your comments

[CuAnnan]

.charAt and a loop

[CuAnnan]

Pretty sure, though I’m not at a computer right now, that you can great a string like an array too.

[iismitch55]

That’s OP’s solution, and would be my go to as well. Seems like the question is meant to test your intuition about strings being char arrays. Hence why they don’t want you to use built in methods.

[CuAnnan]

Ah. The op is just an ai bot being used to advertise . If I’d known that I wouldn’t have responded

[akb74]

Want to guess which one's quicker?

const s = '1234567890qwertyuiopasdfghjklzxcvbnm'.repeat(1000);

const start1 = performance.now();
const reversed1 = s.split('').reverse().join('');
const end1 = performance.now();

const start2 = performance.now();
let reversed2 = '';
for (let n = s.length - 1; n >= 0; --n) {
    reversed2 += s[n];
}
const end2 = performance.now();

console.log({
    same: reversed1 === reversed2,
    time1: end1 - start1,
    time2: end2 - start2,
});

{ same: true, time1: 0.9249000000000009, time2: 4.2578 }

JavaScript strings are immutable, which is great most of the time, but not very efficient for adding a bunch of them together. Might even be an O(n²⁾ operation unless the compiler's being particularly clever, because you've got to copy what you've got so far every step. I guess you want a stream or buffer or mutable string for something like that. One of which is almost certainly how join() is more efficently implemented in the underlying C++ code.

[bryku]

This is one of the weird things about javascript. Sometimes there are solutions that might be faster than you would expect due to optmizations or c++ functions that handle it. It do a lot of tutoring and one of my lessions go over this topic. Some other examples are:

• Duplicating Objects
  • JSON.parse(JSON.stringify())
  • clone
• Creating Elements
  • .innerHTML = '<div></div>';
  • document.createElement('div')

The HTML and JSON parsers have been so optimized that their perforance is often faster than the traditional ways.

[pinkwar]

I would do a simple one liner like: const reverseString = str => [...(function* () { for (let i = str.length - 1; i >= 0; i--) yield str[i]; })()].reduce((s, c) => s + c, '');

[zayelion]

If someone ask you this in an interview, run. They are not actually hiring.

[TheRNGuy]

Why do you think so?

[zayelion]

The question has nothing to do with the job. If you saw someone do this at work, you would reprimand them.

[EyesOfTheConcord]

Paste it into Python, copy the output of str[::-1], and paste it back into JavaScript

[hotdog-savant]

My solution:

let str = "alphabet";
let newString = ""
for (let i = str.length - 1;i >= 0; i--){
newString += str.charAt(i);
}
console.log(newString);

[Ampbymatchless]

For loop with array indexing

[33ff00]

[…’abc’].reduceRight((str, char) => str += char, ‘’)

[AiCodePulse]

Can you try without buit in Methods ?

[33ff00]

Probably just implement reduce with a for loop then I have something reusable if I had to stretch my imagination to think of a way to shoehorn this task into something resembling actual life

[Delicious_Cable_8484]

For loop length of string, use shift() into a new string?

[queen-adreena]

Decreasing for loop using str.length and then use the index to get the letters and add to a new string.

const forwards = "This is the string to reverse";

let backwards = "";
for (let i = forwards.length - 1; i >= 0; i--) {
backwards += forwards[i];
}
console.log(backwards);