Flatten array inside array

Question

I have an array of objects, where each object has a "standings" property (example data below). I want to flatten the standings array and add it to the end of the parent object.

[{
name: "Entry 1",
value: 0,
standings: [{
    week: 1,
    team: 'MIN'
    }, {
    week: 2,
    team: 'NE'
    }, {
    week: 3,
    team: null
    }]
}, {
name: "my Other Entry",
value: 3,
standings: [{
    week: 1,
    team: 'BUF'
    }, {
    week: 2,
    team: 'CIN'
    }, {
    week: 3,
    team: 'TB'
    }]
}];

How can I get:

[{name: "Entry 1", value: 0, w1: 'MIN', w2: 'NE', w3: null},
{name: "my Other Entry", value: 3, w1: 'BUF', w2: 'CIN', w3: 'TB'}]

I was thinking some variation of flatten?

Do you want to do it programmatically in javascript? Or you are looking for suggestions to name your flat json? — Carlos Calla
– Carlos Calla, Commented Sep 10, 2015 at 17:30

Nina Scholz · Accepted Answer · 2015-09-10 17:46:49Z

A Array.prototype.reduce will do:

var data = [
        {
            name: "Entry 1",
            value: 0,
            standings: [{
                week: 1,
                team: 'MIN'
            }, {
                week: 2,
                team: 'NE'
            }, {
                week: 3,
                team: null
            }]
        }, {
            name: "my Other Entry",
            value: 3,
            standings: [{
                week: 1,
                team: 'BUF'
            }, {
                week: 2,
                team: 'CIN'
            }, {
                week: 3,
                team: 'TB'
            }]
        }
    ],
    data1 = data.reduce(function (r, a) {
        r.push(a.standings.reduce(function (rr, b) {
            rr['w' + b.week] = b.team;
            return rr;
        }, {
            name: a.name,
            value: a.value
        }));
        return r;
    }, []);
document.write('<pre>'+JSON.stringify(data1, 0, 4)+'</pre>');

Tony · Accepted Answer · 2015-09-10 17:35:10Z

1

I don't think _.flatten will help much here considering your data structure.

Without the use of a library you can just loop over your data and convert it manually:

function collapseStandings() {
    var formattedData = [];
    data.forEach(function(entry) { // data is your sample data.
        var convertedObj = {
            name: entry.name,
            value: entry.value
        };
        entry.standings.forEach(function(standing){
            convertedObj['w' + standing.week] = standing.team;
        });

        formattedData.push(convertedObj);                   
    });

    return formattedData;
}

Complete fiddle.

answered Sep 10, 2015 at 17:35

Tony

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