Breaking strings in an array into subarrays

Question

Doing the DNA challenge and so close but clearly misunderstanding prototype.split(""). What's the best way to turn these strings ["AC", "CA", "TA"] into subarrays? [["A","C"]["C","A"]["T","A"]]

function pairElement(str) {
  //break into array
  var arr = str.split("");

  //add new letter (could be refactored as switch)
  for (i = 0; i < arr.length; i++) {
    if (arr[i] == "G") {
      arr[i] += "C";
    } else if (arr[i] == "C") {
      arr[i] += "G";
    } else if (arr[i] == "T") {
      arr[i] += "A";
    } else if (arr[i] == "A") {
      arr[i] += "T";
    }
  }

  //break into arrays again
  //this is how I'm trying to use.split to break it up. Doesn't work.
  var broken = [];
  for (x = 0; x < arr.length; x++) {
    broken += arr[x].split("");
  }

  //return
  return arr;
}

console.log(pairElement("GCG"));

Muhammad Usman · Accepted Answer · 2018-05-04 21:37:26Z

3

you can use .map and split them by ""

var o =  ["AC", "CA", "TA"];

var s =  o.map(e=> e.split(""));

console.log(s)

answered May 4, 2018 at 21:37

Muhammad Usman

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Comments

tjadli · Accepted Answer · 2018-05-04 21:37:06Z

2

You actually have to just push the split result in the broken array and return it !

function pairElement(str) {
  //break into array
  var arr = str.split("");

  //add new letter (could be refactored as switch)
  for (i = 0; i < arr.length; i++) {
    if (arr[i] == "G") {
      arr[i] += "C";
    } else if (arr[i] == "C") {
      arr[i] += "G";
    } else if (arr[i] == "T") {
      arr[i] += "A";
    } else if (arr[i] == "A") {
      arr[i] += "T";
    }
  }

  //break into arrays again
  //this is how I'm trying to use.split to break it up. Doesn't work.
  var broken = [];
  for (x = 0; x < arr.length; x++) {
    broken.push(arr[x].split(""));
  }

  //return
  return broken;
}

console.log(pairElement("GCG"));

answered May 4, 2018 at 21:37

tjadli

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2 Comments

chauxvive Over a year ago

This may not be the neatest syntax but you get the answer because you're totally right yaaaaay! Thank you!

tjadli Over a year ago

Well the point is for you to understand where the problem is ! and from there you can optimize your code!

Jonny Rathbone · Accepted Answer · 2018-05-04 21:36:32Z

1

To answer your 'what's the best way' question, map your arrays into the split versions of themselves:

const subarrays = array.map(pair => pair.split());

answered May 4, 2018 at 21:36

Jonny Rathbone

1797 bronze badges

Comments

bipll · Accepted Answer · 2018-05-04 21:38:37Z

1

Very simple in functional style:

> seq = ['AC', 'CA', 'TA']
[ 'AC', 'CA', 'TA' ]
> seq.map(s => s.split(''))
[ [ 'A', 'C' ], [ 'C', 'A' ], [ 'T', 'A' ] ]

answered May 4, 2018 at 21:38

bipll

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1 Comment

chauxvive Over a year ago

Good to see a clean way of doing this. Thank you!

score 1 · Accepted Answer · 2018-05-04 22:11:33Z

Overall, I'd do some refactoring on the whole function:

var m = new Map([["G", "C"], ["C", "G"], ["A", "T"], ["T", "A"]]);

function pairElement(str) {
  return [...str].map(c => [c, m.get(c)]);
}

console.log(pairElement("GCG"));

And if there's a guarantee that the sub-arrays are never mutated, then you can save a good bit of memory by reusing arrays instead of creating them over and over.

var m = new Map([["G", ["G", "C"]], ["C", ["C", "G"]], ["A", ["A", "T"]], ["T", ["T", "A"]]]);

function pairElement(str) {
  return [...str].map(c => m.get(c));
}

console.log(pairElement("GCG"));

But to directly answer your question, you can do it without explicit .split() calls. Since you know there's always two characters, you can use parameter destructuring on the strings.

var arr = ["AC", "CA", "TA"];

var s = arr.map(([a, b]) => [a, b]);

console.log(s)

Or even a little shorter using rest syntax, like this:

var arr = ["AC", "CA", "TA"];

var s = arr.map(([...a]) => a);

console.log(s)

Or using spread syntax in an array literal:

var arr = ["AC", "CA", "TA"];

var s = arr.map(s => [...s]);

console.log(s)

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