Javascript concatenate rows based on column-CodePudding

I have a feeling this question already exists, just can't find it. Is there a way to take a 2d array with x rows and 2 columns and merge multiple values into one row based on it having the same element in the first column?

[['Needs Work', 'Joe'], ['Needs Work', 'Jill'], ['Needs Work', 'Jack'], ['Complete', 'Sean'], ['Complete', 'Joe'], ['Not Started', 'Laura'], ['Needs Work', 'Jack']]

So that it looks like this

[ [ 'Needs Work', 'Joe,Jill,Jack,Jack' ],
  [ 'Complete', 'Sean,Joe' ],
  [ 'Not Started', 'Laura' ] ]

CodePudding user response：

Considering the answer that you posted, I wrote the following function:

function create_union_array(initial_array) {
  const temporal_object = {};
  for (i in initial_array) {
    const work_state = initial_array[i][0];
    const people_name = initial_array[i][1];
    if (temporal_object[work_state] == undefined) {
      temporal_object[work_state] = [people_name]
    } else {
      temporal_object[work_state].push(people_name)
    }
  }
  const output_array = [];
  let iteration = 0;
  for (i in temporal_object) {
    output_array[iteration] = [i, temporal_object[i]]
    iteration  ;
  }
  return output_array;
}

Unlike yours, instead of returning the names in a concatenated string, this one returns the names in an array, in case you need to work with the names afterwards this would be a better option.

CodePudding user response：

Not sure if this the most efficient way.

function myFunction() {
  var array = [['Needs Work', 'Joe'], ['Needs Work', 'Jill'], ['Needs Work', 'Jack'], ['Complete', 'Sean'], ['Complete', 'Joe'], ['Not Started', 'Laura'], ['Needs Work', 'Jack']];
  const extractColumn = (arr, n) => arr.map(row => row[n])
  var list = [...new Set(extractColumn(array, 0))]//gets set of distict values from first column
  // console.log(list)
  var condensedArray = []
  for (var i = 0; i < list.length; i  ) {
    var filteredArray = array.filter(row => row[0] == list[i])//filters array to only to current value
    // console.log(filteredArray)
    condensedArray.push([list[i], extractColumn(filteredArray, 1).toString()])

  }
  console.log(condensedArray)
}