🚩 Remember to use Read-Search-Ask if you get stuck. Try to pair program 👥 and write your own code 📝

• 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.

• Array.push()
• String.split()

• There are two base case, A-T and C-G, these go both way. You can use regular expression, if statements of anything that you can think of.

try to solve the problem now

• I would recommend using a switch, as it makes things a lot smoother.

try to solve the problem now

• The result must be an array of arrays, so keep that in mind when pushing things.

try to solve the problem now

Solution ahead!

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");

🚀 Run Code

• The program is very simple, the best solution that I have come up with is to use a switch to catch all the possible four elements. Using if statements would take too much code. You could also use Regular Expressions.
• Since we have to the original and the pair, I decided to take all four cases instead of the base two.
• Create an empty array and use the search function to push the right values to the array and return them.

• Switch Statements

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;
}

// test here
pairElement("GCG");

🚀 Run Code

• First define an object with all pair possibilities, this allows us to easily find by key or value.
• Split str into a characters array so we can use each letter to find its pair.
• Use a loop to go throw the array of characters and replace each character by an array of the pair, thus creating 2d arrays.

• Bracket Notation for objects

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