1 line of code: How to reverse a string

const reverseString = str => [...str].reverse().join("");

Returns the reversed string.

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The repository & npm package

You can find the all the utility functions from this series at github.com/martinkr/onelinecode
The library is also published to npm as @onelinecode for your convenience.

The code and the npm package will be updated every time I publish a new article.

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Comments

[Martin Krause]

Hi everyone,

thanks to everyone for the efortand the thoughtful contributions.
I setup a benchmark with all one-line contributions. For me, on chrome, the article's function is the fastest with 400 ops/s.
Interested to see which results you guys get

[Adam Crockett]

I prefer to hard code my reversed strings 🥁

[Frank Wisniewski]

the fastest solution in one line:

const reverseString=([firstChar,...str])=>firstChar?reverseString(str)+firstChar:''  

It's a nice game to write functions in one line. But nothing more...

const areverseString=([firstChar,...str])=>firstChar?areverseString(str)+firstChar:''
//duration of 1.000.000 calls = 478 ms 

const breverseString = str => [...str].reverse().join("");
//duration of 1.000.000 calls = 1210 ms 

const creverseString = str => [...str].reduce((a,c) => c.concat(a));
//duration of 1.000.000 calls = 943 ms 

//now the classical way....
const reverseString = function (str) {
  let length = str.length
  let reverse = ''
  for (let i = 0; i<length; i++ ){
    reverse = str[i] + reverse
  }
  return reverse
}
//duration of 1.000.000 calls = 210 ms 

let start = performance.now()  
for (let y=1; y<1000000 ;y++){
  reverseString('Sauerkrauttopf');
}
let duration = performance.now() - start;
console.log(duration)

[Alex Lohr]

If this was about speed, it would probably be faster not to use an array at all:

const reverseString = str => { for (let r = '', i = str.lenght; i >= 0;) r += str[--i]; return r }

[Frank Wisniewski]

Uncaught ReferenceError: r is not defined...

[Alex Lohr]

My bad, typed that on the cellphone.

const reverseString = str => { let r = ''; for (let i = str.lenght; i >= 0;) r += str[--i]; return r }

[Frank Wisniewski]

The function doesn't return anything...it seems to be an old turntable phone..;-)

[Alex Lohr]

I'll try it later when I have my PC.

Found the issue, but it is indeed slower.