JavaScript: Condense array by only keeping unique values and their respective counts

Question

JavaScript: Condense array by only keeping unique values and their respective counts

I've taken on a challenging puzzle to solve. I have a multi-dimensional array in my Javascript code that is structured like this; Each feature is defined by an ID, a date (in string format), and a state.

Here's an example:

Features = [
    [1, "20200503", "Active"],
    [2, "20200503", "Closed"],
    [2, "20200503", "Closed"],
    [2, "20200502", "Closed"],
    [2, "20200501", "Active"],
    [2, "20200430", "Active"],
    [2, "20200430", "Active"],
    [3, "20200503", "New"],
    [3, "20200502", "New"],
];

My goal is to condense this array into a new one with the following result;

Features = [
    [1, 1, "Active"],
    [2, 3, "Closed"],
    [2, 3, "Active"],
    [3, 2, "New"],
];

I'm looking to perform a distinct operation based on the ID and state while counting the occurrences of each date.

Is it feasible to achieve this using Javascript?

javascript arrays count distinct

Answer 1

Answer №1

To achieve the desired outcome, you should utilize the reduce method to condense the array. Thankfully, there exists a handy function for this exact purpose! By providing an empty array as the second argument of the reduce function, you can use it as an accumulator and compare the current element with the previous one to determine the necessary actions.

data = data.reduce((accumulator, current, index, array) => {
  let previous = array[index - 1];

  if (index === 0 || current[0] !== previous[0] || current[2] !== previous[2]) accumulator.push([current[0], 1, current[2]]);
  else accumulator[accumulator.length - 1][1]++;

  return accumulator;
}, []);

Answer 2

To achieve the desired outcome, you should utilize the reduce method to condense the array. Thankfully, there exists a handy function for this exact purpose! By providing an empty array as the second argument of the reduce function, you can use it as an accumulator and compare the current element with the previous one to determine the necessary actions.

data = data.reduce((accumulator, current, index, array) => {
  let previous = array[index - 1];

  if (index === 0 || current[0] !== previous[0] || current[2] !== previous[2]) accumulator.push([current[0], 1, current[2]]);
  else accumulator[accumulator.length - 1][1]++;

  return accumulator;
}, []);

Answer 3

Answer №2

function condenseAttrs(attributes) {
    // Retrieve unique identifiers and states
    var ids = new Set(attributes.map(attr => attr[0]);
    var states = new Set(attributes.map(attr => attr[2]);

    // Initialize array to store the condensed result
    const condensedResult = [];

    // Iterate through all permutations of IDs and States
    for (const id of ids) {
        for (const state of states) {
            // Count number of attributes with matching id and state
            let attrCount = attributes.filter(attr => attr[0] === id && attr[2] === state).length;
            
            // Check if there are any attributes with ID "id" and State "state"
            if (attrCount > 0)
                condensedResult.push([id, attrCount, state]);
        }
    }
    
    return condensedResult;
}

Invoke the function like this

var compressedAttributes = condenseAttrs(Attributes);

Answer 4

function condenseAttrs(attributes) {
    // Retrieve unique identifiers and states
    var ids = new Set(attributes.map(attr => attr[0]);
    var states = new Set(attributes.map(attr => attr[2]);

    // Initialize array to store the condensed result
    const condensedResult = [];

    // Iterate through all permutations of IDs and States
    for (const id of ids) {
        for (const state of states) {
            // Count number of attributes with matching id and state
            let attrCount = attributes.filter(attr => attr[0] === id && attr[2] === state).length;
            
            // Check if there are any attributes with ID "id" and State "state"
            if (attrCount > 0)
                condensedResult.push([id, attrCount, state]);
        }
    }
    
    return condensedResult;
}

Invoke the function like this

var compressedAttributes = condenseAttrs(Attributes);

JavaScript: Condense array by only keeping unique values and their respective counts

Answer №1

Answer №2

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