Leveraging functions in a Node.js module

Question

Leveraging functions in a Node.js module

I am struggling with using a function inside a Node.js module. I have implemented a custom sorting function to sort an array of objects based on the value of a specific property.

exports.getResult = function(cards) {
    cards.sort(sortByField('suit'));
    ...
    ...
    ...
    return cards;
}

function sortByField(fieldName) {
    return function(card1, card2) {
        return card1[fieldName] < card2[fieldName]
    };
}

When I use the getResult function without exporting it and call it from the same file, everything works correctly. The object with the highest suit value appears first, and the one with the lowest value appears last.

However, when I export the function from my index.js file and then call it, the sorting does not take place. There are no errors, but the array remains in the original order after the function executes.

I've tried various solutions such as module.exports.sortByField() and requiring .sortByField() in a separate module, but I still can't find the solution. There must be a simple answer, but it's eluding me.

javascript node.js

Answer 1

Answer №1

It seems that the functionality is consistent in both scenarios, but the issue lies within the sort callback.

According to documentation, a sort callback should not return boolean values, but rather a negative number, 0, or a positive number: A negative number indicates the first entry comes before the second, 0 denotes they are equal, and a positive number signifies the first entry comes after the second.

If the elements in cards are numerical, you should use:

return card1[fieldName] - card2[fieldName];

...for ascending sorting.

For strings, consider using localeCompare:

return card1[fieldName].localeCompare(card1[fieldName]);

Answer 2

It seems that the functionality is consistent in both scenarios, but the issue lies within the sort callback.

According to documentation, a sort callback should not return boolean values, but rather a negative number, 0, or a positive number: A negative number indicates the first entry comes before the second, 0 denotes they are equal, and a positive number signifies the first entry comes after the second.

If the elements in cards are numerical, you should use:

return card1[fieldName] - card2[fieldName];

...for ascending sorting.

For strings, consider using localeCompare:

return card1[fieldName].localeCompare(card1[fieldName]);

Answer 3

Answer №2

As a newcomer to all of this, I must admit that the code I originally shared was not the root of the issue. In short, the array passed to the getResult() function consisted of arrays instead of objects.

My mistake was adding cards to an array of played cards using the following code:

playedCards.push(game.playCard(1, players[0].hand, 3));

The playCard() function was returning an array:

exports.playCard = function(amount, hand, index) {
    const cards = hand.splice(index, amount);
    return cards;
};

However, it should have returned an individual object instead:

exports.playCard = function(amount, hand, index) {
    const cards = hand.splice(index, amount);
    return cards[0];
};

Answer 4

As a newcomer to all of this, I must admit that the code I originally shared was not the root of the issue. In short, the array passed to the getResult() function consisted of arrays instead of objects.

My mistake was adding cards to an array of played cards using the following code:

playedCards.push(game.playCard(1, players[0].hand, 3));

The playCard() function was returning an array:

exports.playCard = function(amount, hand, index) {
    const cards = hand.splice(index, amount);
    return cards;
};

However, it should have returned an individual object instead:

exports.playCard = function(amount, hand, index) {
    const cards = hand.splice(index, amount);
    return cards[0];
};

Leveraging functions in a Node.js module

Answer №1

Answer №2

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