DNA Pairing——Easy algorithm challenge

Problem Explanation:

You will get a DNA strand sequence and you need to get the pair and return it as a 2D array of the base pairs. Keep in mind that the provided strand should be first always.

pairElement("ATCGA") should return [["A","T"],["T","A"],["C","G"],["G","C"],["A","T"]].
pairElement("TTGAG") should return [["T","A"],["T","A"],["G","C"],["A","T"],["G","C"]].
pairElement("CTCTA") should return [["C","G"],["T","A"],["C","G"],["T","A"],["A","T"]].

basic solution:

function pairElement(str) {
  // Return each strand as an array of two elements, the original and the pair.
  var paired = [];

  // Function to check with strand to pair.
  var search = function(char) {
    switch (char) {
      case 'A':
        paired.push(['A', 'T']);
        break;
      case 'T':
        paired.push(['T', 'A']);
        break;
      case 'C':
        paired.push(['C', 'G']);
        break;
      case 'G':
        paired.push(['G', 'C']);
        break;
    }
  };

  // Loops through the input and pair.
  for (var i = 0; i < str.length; i++) {
    search(str[i]);
  }

  return paired;
}

// test here
pairElement("GCG");

Intermediate Code Solution:

function pairElement(str) {
  //define a map object with all pair possibilities 
  var map = {T:'A', A:'T', G:'C', C:'G'};
  //split str into a char Array
  strArr = str.split('');
  //replace each Array item with a 2d Array using map
  for (var i=0;i<strArr.length;i++){
    strArr[i]=[strArr[i], map[strArr[i]]];
  }
 return strArr;
}

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