Critique my JS solution to this CodeWars Kata
#help#javascript
Salim MAHBOUBI

Salim MAHBOUBI @ztickm

About: Frontend developer, Featherless biped

Location:
Germany
Joined:
Feb 16, 2017

Critique my JS solution to this CodeWars Kata

Publish Date: Mar 7 '18
13 9

The Kata

The exercice basically asks to convert any 'T' to 'A' any 'C' to 'G' and vice versa for any given string.

My solution

I know it might not be the exemplary solution but it was the first thing that popped in my head.
I wrote it first like this:

function DNAStrand(dna){
let map = Array.prototype.map;
let reversedDna = map.call(dna, function(x) { 
  let y;
  switch(x){
    case 'A': y = 'T'; break;
    case 'T': y = 'A'; break;
    case 'G': y = 'C'; break;
    case 'C': y = 'G'; break;
  }
  return y; 
});
return reversedDna.join('');
}
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then I thought to myself: "I can remove that y variable." So I did:

function DNAStrand(dna){
let map = Array.prototype.map;
let reversedDna = map.call(dna, function(x) { 
  let y;
  switch(x){
    case 'A': return 'T'; break;
    case 'T': return 'A'; break;
    case 'G': return 'C'; break;
    case 'C': return 'G'; break;
  }
});
return reversedDna.join('');
}
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Then I thought: "I can get rid of the break lines since the return statements are already breaking, can't I?"

function DNAStrand(dna){
let map = Array.prototype.map;
let reversedDna = map.call(dna, function(x) { 
  let y;
  switch(x){
    case 'A': return 'T'; 
    case 'T': return 'A'; 
    case 'G': return 'C'; 
    case 'C': return 'G'; 
  }

});
return reversedDna.join('');
}
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Is there any way to improve my solution? Do you have another way of doing that? Leave your remarks in the comments

Comments 9 total

  • Meghan (she/her)
    Meghan (she/her)Mar 7, 2018
    function DNAStrand(dna) {
    return dna.split('').reduce((ac,cv) => {
        switch(cv) {
            case 'A': return ac+'T';
            case 'T': return ac+'A';
            case 'G': return ac+'C';
            case 'C': return ac+'G';
            default:  return ac+cv;
        }
    }, '');
}
    • Salim MAHBOUBI
      Salim MAHBOUBIMar 7, 2018

      Thanks Sean ! I don't know why I didn't think of reduce...

  • Dian Fay
    Dian FayMar 7, 2018
    const lookup = {
  'A': 'T',
  'T': 'A',
  'G': 'C',
  'C': 'G'
};

function DNAStrand(dna) {
  return [...dna].reduce((reversed, nucleotide) => {
    return reversed + lookup[nucleotide];
  }, '');
}

    Defaulting to const declarations helps keep track of what's allowed to change. reduce is more appropriate when you need to accumulate results than the two-step of generating a new array and joining it. The hashtable lookup keeps the reducer body as short as possible, but there's nothing wrong with a switch per se.

    • Donald Merand
      Donald MerandMar 7, 2018

      @dmfay This is a very elegant solution! I like that you're explaining the reasons why you did things like use a const etc.

      One thing you didn't mention is the use of the spread syntax ([...dna]), which is definitely handy in JS when passing arrays around.

    • Moe
      MoeMar 7, 2018

      wow I didn't know 

      [ ...dna]

      would automatically turn your string into an array. I always use 

       dna.spilt("")

      I'm gonna change my solution to reflect this newfound knowledge.

    • Isaac Lyman
      Isaac LymanMar 7, 2018

      Came to the comments to post this exact solution. Very elegantly done.

    • Salim MAHBOUBI
      Salim MAHBOUBIMar 7, 2018

      Clever!
      Thanks Dian!

  • Moe
    MoeMar 7, 2018

    I see no problem with your solution. I like how you iteratively improved your solution.

    Here is my solution. 

    var complements = { A: 'T', T:'A', C: 'G', G: 'C'}

function DNAStrand(dna){
var dnaArray = [...dna]; //turns string into arrary , where each character is an element

 var complementArray = dnaArray.map(x => complements[x]) //maps each character with it's complement and puts the result in an array

 return complementArray.join("") //turn array into a string

}

    or in one line

    var complements = { A: 'T', T:'A', C: 'G', G: 'C'}

function DNAStrand(dna){
 return  [...dna].map(x => complements[x]).join("")
}
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