DNA Pairing- Need help

JavaScript
1

Tell us what’s happening:

What else do i need to do here?

Your code so far

function pairElement(str) {
  
  var arr = str.split("");
  console.log(arr);

  var newArr = [];

  for (i = 0; i < arr.length; i++) {
  arr.forEach(function(item) {
    newArr.push([item[i], item[i+1]]);
  })
    return newArr;
  }

}

pairElement("GCG");

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:62.0) Gecko/20100101 Firefox/62.0.

Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/dna-pairing

2

Yes! I was able to do it:

function pairElement(str) {
  
  var arr = str.split("");
  console.log(arr);

  var newArr = [];

  for (i = 0; i < arr.length; i++) {
  if (arr[i] == 'G') {
    newArr.push([arr[i], 'C']);
  }

  else if (arr[i] == 'C') {
    newArr.push([arr[i], 'G']);
  }

  else if (arr[i] == 'A') {
    newArr.push([arr[i], 'T']);
  }

  else {
    newArr.push([arr[i], 'A']);
  }
  }
  return newArr;

}

pairElement("ATCGA");
3

Good job.

(i = 0 …)
This will create a global variable, declare the variable in the initialization (var i = 0), or before the loop inside the function.

Looking at the OP, i just want to point out that you can get the index inside a forEach by passing the index to the callback function

someArray.forEach( function(element, index) {

});

4

You mean I wouldn’t need a for loop if I pass the index as an argument?

5

Yes, you get access to the index of the array inside the forEach.
But you don’t even need the index:

function pairElement(str) {

  var arr = str.split("");
  var newArr = [];

  arr.forEach((ele) => {

      if (ele == 'G') {
        newArr.push([ele, 'C']);
      } else if (ele == 'C') {
        newArr.push([ele, 'G']);
      } else if (ele == 'A') {
        newArr.push([ele, 'T']);
      } else {
        newArr.push([ele, 'A']);
      }

  });
  return newArr;
}