Creating Sorted Rows with JavaScript

Question

At my wits end, I think I may be going code blind but can't for the life of me figure out what is causing the issue.

The desired outcome is for there to be only one date per row in the data array and as many flights for each date.

This works for the first item, but not any of the others, ending up with duplicate dates.

Where am I going wrong?

Desired data: example in coming data 5 objects, only two dates.

["2020-02-20", "LGW"]
["2020-02-20", "LTN"]
["2020-02-20", "LHR"]
["2020-02-26", "LTN"]
["2020-02-26", "LHR"]

an array of two objects (one for each date), with the flights an array by date in the respective date object.

data = [ ["2020-02-20", ["LGW","LTN","LHR"]],
["2020-02-26", ["LTN","LHR"]]
]

Code shown below with comments:

function getRows(alternatives) {
        var data = [];

        for (var i = 0; alternatives.length > i; i++) {
            var tmp = new Date(parseInt(alternatives[i].substring(0, 10)) * 1000);
            var month = (tmp.getMonth() + 1);
            var date = tmp.getFullYear() + "-" + (month < 10 ? "0" + month : month) + "-" + tmp.getDate();
            var airport = alternatives[i].slice(11, 14);

            var rowData = {
                date: date,
                flights: []
            };
            // if data has objects, check to see if the date is in any of the objects, if it isn't then add rowData to data
            if (data.length > 0) {

                for (var j = 0; data.length > j; j++) {

                    if (data[j].date === rowData.date) {
                        //if there are no flights, add the airport, if there are, is the airport already there, if not, add it
                        if (data[j].flights.length > 0 || !data[j].flights.includes(airport)) {
                            data[j].flights.push(airport);
                        }
                    }
                    else {
                        data.push(rowData);
                        continue;
                    }
                }
            }
            else {
                rowData.flights.push(airport);
                data.push(rowData);
            }
        }
        // not working, dupe dates are appearing in the rows
        return data;
    }

Just a note that it can be helpful to show an example of the data structure you want to see vs. the data structure it's currently giving you. Helps avoid misunderstanding about your data. — canpan14
– canpan14, Commented Jul 23, 2019 at 16:58

random · Accepted Answer · 2019-07-23 17:18:14Z

1

You can use reduce, create the object which has date as key with value consisting of array with date and array of flights. Check if key already exist, if present then only push in the flights array.

const input = [["2020-02-20", "LGW"],
["2020-02-20", "LTN"],
["2020-02-20", "LHR"],
["2020-02-26", "LTN"],
["2020-02-26", "LHR"]];

const output = Object.values(input.reduce((accu, [date, flight]) => {
    if(!accu[date]) {
        accu[date] = [date, [flight]];
    } else {
        accu[date][1].push(flight);
    }
    return accu;
}, {}));

console.log(output);

answered Jul 23, 2019 at 17:18

random

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2 Comments

PurpleSmurph Over a year ago

Thank you for your answer, very streamlined. Apologies for the late reply - have been ill - what's accu in your example?

random Over a year ago

@PurpleSmurph - accu stands for accumulator. The initial value of accu is set to empty object {}, which is second parameter to the reduce function, if not provided, the first element in the array will be used. You can check the link - developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… to know more.

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