Combining Javascript Arrays into key value look up

Question

I have a Javascript object called Data that looks like:

Object {
  zip: Array[14631],
  lat: Array[14631],
  lng: Array[14631],
  surge: Array[14631]
}

Data looks like

Zipcode, Lat,    Lng,    Surge
10025,   47.323, -93.43, 1.7

So to access elements I can do something like: data['zip'][i] and it will return the 'ith' element of the zip array. I can do the same with all the arrays.

What I want is a data structure such that I can do: data[10025] and it will return all matching element in the other arrays. So lets say I had 5 entries with zipcode = 10025, the data[10025] would return:

10025,lat_1,lng_1,surge_1
10025,lat_2,lng_2,surge_2
10025,lat_3,lng_3,surge_3
10025,lat_4,lng_4,surge_4
10025,lat_5,lng_5,surge_5

So that I could then double iterate through

for zip in data['zip']{
  for i in data[zip] {
    print data[zip]['lats'][i]
  }
}

I think this is a simple enough problem but I don't have much experience with javascript and can't seem to get it. Any help is much appreciated.

Another way to phrase this is I would like an object that looks like:

    data[array size of N]

Where each element of that array holds 3 arrays of size M

What parts do you think I should add? The real structure is an object with 4 arrays of equal length. — William Calhoun
– William Calhoun, Commented May 27, 2016 at 18:25

James Reimer · Accepted Answer · 2016-05-27 18:36:28Z

2

Why not do it something like this...

data = {
    "10025": [
        {
            "Lat": 47.323,
            "Lng": -93.43,
            "Surge": 1.7
        },{
            "Lat": 47.323,
            "Lng": -93.43,
            "Surge": 1.7
        },{
            "Lat": 47.323,
            "Lng": -93.43,
            "Surge": 1.7
        }
    ]
};

Then you could access the zip by data["10025"] and loop through the array of locations.

var data = {};
for(var i = 0; i < obj.zip.length;i++){
    var zip = obj.zip[i]
    data[zip] = data[zip] || [];
    data[zip].push({
        zip: obj.zip[i],
        lat: obj.lat[i],
        lng: obj.lng[i],
        surge: obj.surge[i]
    });
}

edited May 27, 2016 at 18:36

user2033671

answered May 27, 2016 at 18:25

James Reimer

1961 silver badge6 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

William Calhoun Over a year ago

Ideally that would be the best way to do it. But the data is given to me in the format I described. I want to turn it into the format you describe above.

user2033671 Over a year ago

James, I added the algorithm to achieve your proposed data structure. Feel free to roll back the edit if you do not agree.

William Calhoun Over a year ago

Thanks guys, that did the trick. Is there an easy way I can iterate through the zipcodes now that they a keys?

user2033671 Over a year ago

Object.keys(data)

Nina Scholz · Accepted Answer · 2016-05-27 18:37:42Z

2

Without changing the original data, you could use the indices of the array in a new array for an object with the zip code as key.

data = {
    "10025": [ 2, 4, 7, 10],
    "10027": [ 1, 3, 9, 11],
};

Generate data with

var data = Object.create(null); // create empty object

object.zip.forEach(function (z, i) {
    data[z] = data[z] || [];
    data[z].push(i);
});

Access would be:

data[zip].forEach(function (index) {
    // do something with the value ...
    var lat = object.lats[index]
});

edited May 27, 2016 at 18:37

answered May 27, 2016 at 18:32

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

1 Comment

William Calhoun Over a year ago

How would I do that in Javascript given just the object Data, I described?

Sensei James · Accepted Answer · 2016-05-27 18:43:49Z

0

// Array, keyed by zip code
var zip_array = [];

// Iterate over zip data, building zip_array as we go.
var zip_data = data.zip;
for (var i = 0, len = zip_data.length; i < len; ++i)
{
    var current_zip = zip_data[i];
    if (zip_array[current_zip]){
      zip_array[current_zip].push(getDataAt(i));
    }
  else {
    zip_array[current_zip] = [ getDataAt(i) ];
  }
}

function getDataAt (index)
{
  return [ data.zip[index], data.lat[index], data.lng[index], data.surge[index]].join(",");
}

answered May 27, 2016 at 18:43

Sensei James

2,7012 gold badges31 silver badges36 bronze badges

1 Comment

Sensei James Over a year ago

POST QUESTION-UPDATE: If you want zip_array to be a 3d array (as you describe), instead of 2d as I have implemented here, then just omit the .join(",") in the final line of getDataAt.

Collectives™ on Stack Overflow

Combining Javascript Arrays into key value look up

3 Answers 3

4 Comments

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related