Unleashing the power of JavaScript: A guide to dynamically generating nested arrays

Question

Unleashing the power of JavaScript: A guide to dynamically generating nested arrays

Can you take a look at the code below and help me find the mistake?

function pair(str) {

  // Function to pair specific letters in a string

  for (var i = 0; i < str.length; i++) {

    // Check and pair letters based on certain conditions

    if (str[i] == 'G' && str[i - 1] != 'C') {
      str = str.slice(0, i) + 'C' + str.slice(i);
    } else if (str[i] == 'T' && str[i - 1] != 'A') {
      str = str.slice(0, i) + 'A' + str.slice(i);
    } else if (str[i] == 'C' && str[i + 1] != 'G') {
      str = str.slice(0, i + 1) + 'G' + str.slice(i + 1);
    } else if (str[i] == 'A' && str[i + 1] != 'T') {
      str = str.slice(0, i + 1) + 'T' + str.slice(i + 1);
    }
  }

  str = str.split('');

  var temp = [];
  for (var j = 0; j <= str.length / 2; j++) {
    temp.push([]);
    for (var k = 0; k < 2; k++) {
      temp[j].push(str.shift());
    }
  }
  return temp;

}

pair("TTGAG");

The expected output is [['A', 'T'], ['A', 'T'], ['C', 'G'], ['A', 'T'], ['C', 'G']]. However, the actual output is [['A', 'T'], ['A', 'T'], ['C', 'G']]. Can you spot the mistake?

javascript arrays

Answer 1

Answer №1

It appears that the issue has been identified. Essentially, the key is to establish the limit for the outer for loop prior to its execution.

var limit = str.length / 2 -1;
for (var j = 0; j <= limit; j++) {
...

Alternatively,

var limit = str.length / 2;
for (var j = 0; j < limit; j ++) {
...

The rationale behind this is that with each shift operation in the inner loop, the size of the str array decreases by one. The j <= str.length /2 expression is assessed at the start of each loop, after two shifts have already occurred in the prior inner loop.

Initially, str.length / 2 == 5; temp == [['A', 'T']]

Subsequently, following two shift operations, str.length / 2 == 4; temp == [['A', 'T']['A','T']]

After two more shifts, str.length /2 == 3;

temp == [['A','T']['A','T']['C','G']]

Upon the final evaluation of the outer for loop condition, with str.length / 2 == 2, and j == 2, the loop concludes.

For more information on for loops, the MDN reference can be found here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for

Answer 2

It appears that the issue has been identified. Essentially, the key is to establish the limit for the outer for loop prior to its execution.

var limit = str.length / 2 -1;
for (var j = 0; j <= limit; j++) {
...

Alternatively,

var limit = str.length / 2;
for (var j = 0; j < limit; j ++) {
...

The rationale behind this is that with each shift operation in the inner loop, the size of the str array decreases by one. The j <= str.length /2 expression is assessed at the start of each loop, after two shifts have already occurred in the prior inner loop.

Initially, str.length / 2 == 5; temp == [['A', 'T']]

Subsequently, following two shift operations, str.length / 2 == 4; temp == [['A', 'T']['A','T']]

After two more shifts, str.length /2 == 3;

temp == [['A','T']['A','T']['C','G']]

Upon the final evaluation of the outer for loop condition, with str.length / 2 == 2, and j == 2, the loop concludes.

For more information on for loops, the MDN reference can be found here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for

Answer 3

Answer №2

If I understand correctly, you're facing the task of converting an input string like "TTGAG" into an array of [A,T] or [C,G].

Here is the approach I suggest:

// renamed pair function for clarity
// assuming genes == 'TTGAG'
function GeneStringToArray(genes){
    var geneSplit = genes.split(''); // [T,T,G,A,G]

    for(var i = 0; i < geneSplit.length; i += 1){
        geneSplit[i] = getGenePair(geneSplit[i]);      
    }

    return geneSplit; // output: [['A','T'],['A','T'],['C','G'],['A','T'],['C','G']]
}    


function getGenePair(gene) {
    // converting to lowercase for easy comparison
    gene = gene.toLowerCase();

    // Defining results
    var at = ['A', 'T'];
    var cg = ['C','G'];

    if(gene === 'a' || gene === 't'){
        return at;
    }

    if(gene === 'c' || gene === 'g'){
        return cg;
    }
}

I believe this solution provides a clear and readable way to address your issue.

Answer 4

If I understand correctly, you're facing the task of converting an input string like "TTGAG" into an array of [A,T] or [C,G].

Here is the approach I suggest:

// renamed pair function for clarity
// assuming genes == 'TTGAG'
function GeneStringToArray(genes){
    var geneSplit = genes.split(''); // [T,T,G,A,G]

    for(var i = 0; i < geneSplit.length; i += 1){
        geneSplit[i] = getGenePair(geneSplit[i]);      
    }

    return geneSplit; // output: [['A','T'],['A','T'],['C','G'],['A','T'],['C','G']]
}    


function getGenePair(gene) {
    // converting to lowercase for easy comparison
    gene = gene.toLowerCase();

    // Defining results
    var at = ['A', 'T'];
    var cg = ['C','G'];

    if(gene === 'a' || gene === 't'){
        return at;
    }

    if(gene === 'c' || gene === 'g'){
        return cg;
    }
}

I believe this solution provides a clear and readable way to address your issue.

Unleashing the power of JavaScript: A guide to dynamically generating nested arrays

Answer №1

Answer №2

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