How do I create a simple array from an array of array with JavaScript?

Question

I would like to create an array from a multidimensional array like this:

var dataItaly = [
/*Town       Region   City*/
  ["Castelspina","Piemonte","Alessandria"  ],
  ["Cavatore","Piemonte","Alessandria"  ],
  ["Cella Monte","Piemonte","Alessandria"  ],
  ["Cereseto","Piemonte","Alessandria"  ],
  ["Cantarana","Piemonte","Asti"  ],
  ["Capriglio","Piemonte","Asti"  ],
  ["Casorzo","Piemonte","Asti"  ],
  ["Albino","Lombardia","Bergamo"  ],
  ["Algua","Lombardia","Bergamo"  ],
  ["Abbiategrasso","Lombardia","Milano"  ],
  ["Agrate Brianza","Lombardia","Milano"  ],
  ["Aicurzio","Lombardia","Milano"  ],
  ["Almese","Piemonte","Torino"  ],
  ["Alpette","Piemonte","Torino"  ],
  ["Alpignano","Piemonte","Torino"  ],
  ["Andezeno","Piemonte","Torino"  ],
  ["Albonese","Lombardia","Pavia"  ],
  ["Albuzzano","Lombardia","Pavia"  ],
  ["Arena Po","Lombardia","Pavia"  ],
  ["Badia Pavese","Lombardia","Pavia"  ]
];

this is my starting point ...

var region = "Piemonte"
// array must appear the city of "Piemonte"

function createArrayCity (dataItaly, region) {
var arrayList;
for (i = 0; i <dataItaly.length i) {
  if the region === [1] {
    arrayList [2]. append;
return arrayList;
}
}
}

The contents of this must be arrayList [Alessandria, Torino, Asti]. If var region = "Lombardia" the contents of arrayList is [Bergamo, Milano, Pavia]

Guys thanks a lot for the help. For me, the iterations in the array are still a tough nut. Now I have a base for studying — David
– David, Commented May 14, 2013 at 16:31

VisioN · Accepted Answer · 2013-05-13 09:21:58Z

1

I'd do it using .map() and .filter():

var result = dataItaly.map(function(e) {
    return e[1] === region ? e[2] : null;
}).filter(function(e, i, a) {
    return e !== null && a.indexOf(e) === i;
});

N.B.: These methods are rather new and some old browsers might not support them. You should use shims (from here and here) to fix the compatibility.

answered May 13, 2013 at 9:21

VisioN

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Comments

chtenb · Accepted Answer · 2013-05-13 09:24:05Z

1

You can use concat to merge arrays:

var dataItaly = [
  ["Castelspina","Piemonte","Alessandria"  ],
  ["Cavatore","Piemonte","Alessandria"  ],
  ["Cella Monte","Piemonte","Alessandria"  ],
  ["Arena Po","Lombardia","Pavia"  ],
  ["Badia Pavese","Lombardia","Pavia"  ]
];
var merged = [];
merged = merged.concat.apply(merged, dataItaly);

To remove duplicate (if you want that) you could do:

merged = merged.filter (function (v, i, a) { return a.indexOf (v) == i });

edited May 13, 2013 at 9:24

answered May 13, 2013 at 9:18

chtenb

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Comments

Arun P Johny · Accepted Answer · 2013-05-13 09:33:27Z

0

Try

function createArrayCity (dataItaly, region) {
    var arrayList = [];
    for (i = 0; i <dataItaly.length; i++) {
        if (dataItaly[i][1] === region && indexOf(arrayList, dataItaly[i][2]) == -1) {
            arrayList.push(dataItaly[i][2])
        }
    }
    return arrayList;
}

function indexOf(array, obj){
    if(typeof array.indexOf == 'function'){
        return array.indexOf(obj);
    }
    for (i = 0; i <array.length; i++) {
        if(array[i] == obj){
            return i;
        }
    }
    return -1;
}


console.log(createArrayCity(dataItaly, 'Lombardia'))

Demo: Fiddle

edited May 13, 2013 at 9:33

answered May 13, 2013 at 9:28

Arun P Johny

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