DNA Pairing I can't find the problem please help

JavaScript
1

Tell us what’s happening:

This is my code so far,and it can’t get the expected result,so I guess there is something wrong in my code.
result[i]=new Array().push(strArr[i]);
If can’t write like this,Can anyone tell me how to create a new empty array in another array in a loop.

Your code so far


function pairElement(str) {
    function pair(arr){
     switch(arr[0]){
     case "A":
     arr.push("T");
     break;
     case "T":
     arr.push("A");
     break;
     case "C":
     arr.push("G");
     break;
     case "G":
     arr.push("C");
     break;
   }
  }
  let strArr=str.split("");
  let result=[];
  for (let i=0;i<strArr.length;i++){
   result[i]=new Array().push(strArr[i]);
  }
  return result.forEach(pair);
}
pairElement("GCG");

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36.

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

2

You can declare an empty array before and use it like this.

let array = [];
array.push(strArr[i]);

But notice if you are doing this and saving this into result[i], it’s always going to be 1. You need to make sure to push the array after values are pushed into the array.

3 
for (let i=0;i<strArr.length;i++){
     let temp=[];
     temp.push(strArr[i]);
     result[i]=temp;
  }

Sir,as you said,I declared it before i used it.But the result said that
TypeError: Cannot read property 'toString' of undefined
And i can’t find out where the error happens.Can you tell me what happened?

4

Are you using toString method somewhere in your new code?

When I run it with your forloop I am not getting any errors.

function pairElement(str) {
    function pair(arr){
     switch(arr[0]){
     case "A":
     arr.push("T");
     break;
     case "T":
     arr.push("A");
     break;
     case "C":
     arr.push("G");
     break;
     case "G":
     arr.push("C");
     break;
   }
  }
  let strArr=str.split("");
  let result=[];
  for (let i=0;i<strArr.length;i++){
     let temp=[];
     temp.push(strArr[i]);
     result[i]=temp;
  }
  return result.forEach(pair);
}
pairElement("GCG");

It just returns undefined. Try debugging this line.

return result.forEach(pair);

It’s not doing what you are expecting it to do.

1 Like