Understanding how to parse an array of arrays in JavaScript can be a

Question

Understanding how to parse an array of arrays in JavaScript can be a

Looking for a function that can extract a value from an array containing multiple arrays? Simply use getValueFromArray(array, [2, 4]) to get the 4th element of the 2d array within the main array.

Check out the code snippet below:

function getValueFromArray(arr, indexes){

var val,
    currentIndex = indexes[0];

    if(!arr[currentIndex] || arr[currentIndex] === '') return value = '';

    indexes.splice(0, 1);

    if(arr[currentIndex].length) 
        getValueFromArray(arr[currentIndex], indexes);
    else {
        val = arr[currentIndex];
        return val;
    }
 }


      var y = getValueFromArray([[1,2,3,4], [1,2,3,4]], [0, 2]); // should return 3

      var x = getValueFromArray([[1,2,3,4], [1,2,3,4], [5,6,7,8]], [2, 3]); // should return 8

      var z = getValueFromArray(
                           [
                               [[1,2,3,4], [1,2,3,4], [1,2,3,4]],
                               [[1,2,3,4], [1,2,3,4]]
                           ], 
                           [0, 1, 2]
                          ); // should return 3

The function correctly returns the expected value when debugged directly. However, while trying to assign it to a variable, it shows undefined. This issue might be due to recursion. Any suggestions on fixing this?

Appreciate your help!

javascript arrays parsing recursion

Answer 1

Answer №1

Your recursive results are not being properly returned.

if(arr[currentIndex].length) 
    getValueFromArray(arr[currentIndex], indexes);

This code snippet should be adjusted as follows:

if(arr[currentIndex].length) 
    return getValueFromArray(arr[currentIndex], indexes);

Answer 2

Your recursive results are not being properly returned.

if(arr[currentIndex].length) 
    getValueFromArray(arr[currentIndex], indexes);

This code snippet should be adjusted as follows:

if(arr[currentIndex].length) 
    return getValueFromArray(arr[currentIndex], indexes);

Answer 3

Answer №2

There is a small issue in your code where you forgot to return the result after the if condition. You can try using the following updated code:

function getValueFromArray(arr, indexes){

    var val,
        currentIndex = indexes[0];

        if(!arr[currentIndex] || arr[currentIndex] === '') return value = '';

        indexes.splice(0, 1);

        if(arr[currentIndex].length) 
           return getValueFromArray(arr[currentIndex], indexes);
        else {
            val = arr[currentIndex];
            return val;
        }
     }
    var y = getValueFromArray([[1,2,3,4], [1,2,3,4]], [0, 2]);
    console.log(y)

After running this code, you will see that the result is now correctly stored in the variable.

Answer 4

There is a small issue in your code where you forgot to return the result after the if condition. You can try using the following updated code:

function getValueFromArray(arr, indexes){

    var val,
        currentIndex = indexes[0];

        if(!arr[currentIndex] || arr[currentIndex] === '') return value = '';

        indexes.splice(0, 1);

        if(arr[currentIndex].length) 
           return getValueFromArray(arr[currentIndex], indexes);
        else {
            val = arr[currentIndex];
            return val;
        }
     }
    var y = getValueFromArray([[1,2,3,4], [1,2,3,4]], [0, 2]);
    console.log(y)

After running this code, you will see that the result is now correctly stored in the variable.

Answer 5

Answer №3

It is advisable to insert a return statement before calling getValueFromArray(arr[currentIndex], indexes);
This will allow the final calculated value to travel up through the recursive method call stack as each recursive call returns.

Answer 6

It is advisable to insert a return statement before calling getValueFromArray(arr[currentIndex], indexes);
This will allow the final calculated value to travel up through the recursive method call stack as each recursive call returns.

Answer 7

Answer №4

Your answer is spot on. All you needed to do was make sure to include the return statement for the recursive call:

if(arr[currentIndex].length) 
    getValueFromArray(arr[currentIndex], indexes); // <---- here

However, it's worth noting that there is a more concise way to achieve the same result (although this may impact the integrity of the original indexes array):

function getValueFromArray(arr, indexes){
  while(indexes.length) arr=arr[indexes.shift()]
  return arr
}

Answer 8

Your answer is spot on. All you needed to do was make sure to include the return statement for the recursive call:

if(arr[currentIndex].length) 
    getValueFromArray(arr[currentIndex], indexes); // <---- here

However, it's worth noting that there is a more concise way to achieve the same result (although this may impact the integrity of the original indexes array):

function getValueFromArray(arr, indexes){
  while(indexes.length) arr=arr[indexes.shift()]
  return arr
}

Answer 9

Answer №5

The reason for the issue is that the condition is not returning any value. Try using the code below

function getValueFromArray(arr, indexes){

var val='',currentIndex = indexes[0];

    if(!arr[currentIndex] || arr[currentIndex] === '') return val;

    indexes.splice(0, 1);

    if(arr[currentIndex].length) {

       // The problem occurs when the function does not encounter a 'return' statement 
       // and ends up returning nothing.
        return getValueFromArray(arr[currentIndex], indexes);
    }   
    else { 
        val = arr[currentIndex];
        return val;
    }
 }

Afterwards, you can log the variable to the console

var y = getValueFromArray([[1,2,3,4], [1,2,3,4]], [0, 2]);
console.log(y)

Answer 10

The reason for the issue is that the condition is not returning any value. Try using the code below

function getValueFromArray(arr, indexes){

var val='',currentIndex = indexes[0];

    if(!arr[currentIndex] || arr[currentIndex] === '') return val;

    indexes.splice(0, 1);

    if(arr[currentIndex].length) {

       // The problem occurs when the function does not encounter a 'return' statement 
       // and ends up returning nothing.
        return getValueFromArray(arr[currentIndex], indexes);
    }   
    else { 
        val = arr[currentIndex];
        return val;
    }
 }

Afterwards, you can log the variable to the console

var y = getValueFromArray([[1,2,3,4], [1,2,3,4]], [0, 2]);
console.log(y)

Answer 11

Answer №6

I also wanted to share my code because it offers a more straightforward approach to solving the problem at hand.
This solution avoids recursion, potentially resulting in quicker execution.

var arr = [
  [
    [
      [12, 5, 6],
      [ 6, 7, 8],
      [11, 0, 9]
    ],
    [
      [-1, 1, 8],
      [ 4, 5, 6]
    ]
  ],
  [
    [
        [7, 8, 9, 10]
    ]
  ]
];

function getValueFromArray(arr, indexes){
    var value = arr, i = 0, len = indexes.length, index = null;

    for (; i < len; i += 1) {
        index = indexes[i];
        // check if the current array contains an {index}-th record
        if ( index in value ) { 
            value = value[index];
        } else {
            // or throw an exception if you want
            return null;
        }
    }

    return value;
 }

getValueFromArray(arr, [0, 1, 1, 2]) // 6

Answer 12

I also wanted to share my code because it offers a more straightforward approach to solving the problem at hand.
This solution avoids recursion, potentially resulting in quicker execution.

var arr = [
  [
    [
      [12, 5, 6],
      [ 6, 7, 8],
      [11, 0, 9]
    ],
    [
      [-1, 1, 8],
      [ 4, 5, 6]
    ]
  ],
  [
    [
        [7, 8, 9, 10]
    ]
  ]
];

function getValueFromArray(arr, indexes){
    var value = arr, i = 0, len = indexes.length, index = null;

    for (; i < len; i += 1) {
        index = indexes[i];
        // check if the current array contains an {index}-th record
        if ( index in value ) { 
            value = value[index];
        } else {
            // or throw an exception if you want
            return null;
        }
    }

    return value;
 }

getValueFromArray(arr, [0, 1, 1, 2]) // 6

Answer 13

Answer №7

function extractValue(arr, indexes) {
    // Check if the input is valid
    // Exit if arr is not an array or empty
    // Exit if indexes is not an array or empty
    if (!Array.isArray(arr) || !arr.length || !Array.isArray(indexes) || !indexes.length) {
        return; // Handle this case accordingly
    }
    var currentIndex = indexes.shift();
    // Check for valid index
    // Exit if index is out of bounds or negative
    if (arr.length <= currentIndex || currentIndex < 0) {
        return; // Handle this case accordingly
    }
    return Array.isArray(arr[currentIndex]) ? extractValue(arr[currentIndex], indexes) : arr[currentIndex];
}

Answer 14

function extractValue(arr, indexes) {
    // Check if the input is valid
    // Exit if arr is not an array or empty
    // Exit if indexes is not an array or empty
    if (!Array.isArray(arr) || !arr.length || !Array.isArray(indexes) || !indexes.length) {
        return; // Handle this case accordingly
    }
    var currentIndex = indexes.shift();
    // Check for valid index
    // Exit if index is out of bounds or negative
    if (arr.length <= currentIndex || currentIndex < 0) {
        return; // Handle this case accordingly
    }
    return Array.isArray(arr[currentIndex]) ? extractValue(arr[currentIndex], indexes) : arr[currentIndex];
}

Answer 15

Answer №8

Stop overcomplicating things:

function getValueFromArray(arr, indexes){
    return arr[indexes[0]][indexes[1]];
}

Simplified version for 1 to 3 dimensional arrays:

function getValueFromArray(arr, indexes){
    if (indexes.length == 1) {
        return arr[indexes[0]];
    } else if (indexes.length == 2) {
        return arr[indexes[0][indexes[1]];
    } else if (indexes.length == 3) {
        return arr[indexes[0][indexes[1][indexes[2]];
    } else {
      // What about 4 dimensional arrays?
    }
}

Do you really need more than a 3 dimensional array?

Perhaps there's a way to iterate with indexes[i], but it's eluding me at the moment and might not even be feasible.

Answer 16

Stop overcomplicating things:

function getValueFromArray(arr, indexes){
    return arr[indexes[0]][indexes[1]];
}

Simplified version for 1 to 3 dimensional arrays:

function getValueFromArray(arr, indexes){
    if (indexes.length == 1) {
        return arr[indexes[0]];
    } else if (indexes.length == 2) {
        return arr[indexes[0][indexes[1]];
    } else if (indexes.length == 3) {
        return arr[indexes[0][indexes[1][indexes[2]];
    } else {
      // What about 4 dimensional arrays?
    }
}

Do you really need more than a 3 dimensional array?

Perhaps there's a way to iterate with indexes[i], but it's eluding me at the moment and might not even be feasible.

Understanding how to parse an array of arrays in JavaScript can be a

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

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