The error "Cannot invoke the indexOf method on an undefined element at order" is being encountered in Javascript

Question

The error "Cannot invoke the indexOf method on an undefined element at order" is being encountered in Javascript

Looking for assistance with creating a function to sort a string where each word contains a single number from 1 to 9 (no 0).

For instance, given the input: "is2 Thi1s T4est 3a", the desired output should be "Thi1s is2 3a T4est".

The current code snippet:

function order(words)
{
    // ...

    if(words === '')
    {
        return words;
    }

    var all_words = words.split(" ");
    var checked_words = new Array(); 
    var joined_words = "";

    for(i = 1; i <= 9; i++)
    {
        //console.log(checked_words);
        //checked_words[i-1] = all_words;
        for(j = 1;j <= all_words.length; j++)
        {
            if(all_words[i-1].indexOf(i) !== -1)
            {
                checked_words.push(all_words[i-1]);

                if(i == (all_words.length))
                {
                    joined_words = checked_words.join(" ");
                    return joined_words;
                }
            }
        }
    }
}

Encountering an issue of "TypeError: Cannot call method 'indexOf' of undefined at order." Any help would be greatly appreciated. Thank you!

javascript indexof

Answer 1

Answer №1

After some investigation, I've finally come to understand the purpose of that initial loop - it's scanning for numbers within the string. However, this method is not recommended due to its peculiar nature and lack of efficiency if it actually functions as intended.

Instead, a more optimized approach would involve utilizing a single loop in conjunction with a regex pattern to identify the numbers within the string.

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

  // locate the first matching number and convert it to an integer
  var n = +all_words[i].match(/\d+/)[0];
  checked_words[n] = all_words[i];
}

// The 'checked_words' array contains an undefined element at index 0;
// using slice creates a duplicate of the array starting from index 1
return checked_words.slice(1).join(' ');

Check out the DEMO here

An alternative method involves utilizing the reduce function.

var joined_words = str.split(' ').reduce(function (previous, current) {
  var n = +current.match(/\d+/)[0];
  previous[n] = current;
  return previous;
}, []).slice(1).join(' ');

See the corresponding DEMO here

It's worth noting that you can extend this technique beyond just numbers 0-9. As long as you filter out any undefined elements, you'll achieve the desired result...

var str = 'is2 Thi1s T4est 3a Ye12s!';

var output = str.split(' ').reduce(function (previous, current) {
  var n = +current.match(/\d+/)[0];
  previous[n] = current;
  return previous;
}, []).slice(1).filter(function (element) {
  return element !== undefined;
}).join(' ');

View the updated DEMO here

Answer 2

After some investigation, I've finally come to understand the purpose of that initial loop - it's scanning for numbers within the string. However, this method is not recommended due to its peculiar nature and lack of efficiency if it actually functions as intended.

Instead, a more optimized approach would involve utilizing a single loop in conjunction with a regex pattern to identify the numbers within the string.

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

  // locate the first matching number and convert it to an integer
  var n = +all_words[i].match(/\d+/)[0];
  checked_words[n] = all_words[i];
}

// The 'checked_words' array contains an undefined element at index 0;
// using slice creates a duplicate of the array starting from index 1
return checked_words.slice(1).join(' ');

Check out the DEMO here

An alternative method involves utilizing the reduce function.

var joined_words = str.split(' ').reduce(function (previous, current) {
  var n = +current.match(/\d+/)[0];
  previous[n] = current;
  return previous;
}, []).slice(1).join(' ');

See the corresponding DEMO here

It's worth noting that you can extend this technique beyond just numbers 0-9. As long as you filter out any undefined elements, you'll achieve the desired result...

var str = 'is2 Thi1s T4est 3a Ye12s!';

var output = str.split(' ').reduce(function (previous, current) {
  var n = +current.match(/\d+/)[0];
  previous[n] = current;
  return previous;
}, []).slice(1).filter(function (element) {
  return element !== undefined;
}).join(' ');

View the updated DEMO here

The error "Cannot invoke the indexOf method on an undefined element at order" is being encountered in Javascript

Answer №1

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