freeCodeCamp Intermediate Algorithm Scripting: DNA Pairing

pairElement.js

// The DNA strand is missing the pairing element. Take each character, 
// get its pair, and return the results as a 2d array.

// Base pairs are a pair of AT and CG. Match the missing element to the 
// provided character.

// Return the provided character as the first element in each array.

// For example, for the input GCG, return [["G", "C"], ["C","G"],["G", "C"]]

// The character and its pair are paired up in an array, and all the 
// arrays are grouped into one encapsulating array.

function pairElement(str) {
  let myArr={"A" : "T", "T" : "A", "G" : "C", "C" : "G"};
  return str.split("").map(dna => [dna, myArr[dna]] );
}

pairElement("GCG");