Merge dynamic object arrays in javascript

Question

I'm trying to dynamically build an object with key:[value array], however using different methods I keep ending up with a singular item in the value array (where in the response there are multiple values).

Psuedocode:

var myFunction = function () {
    var myObject = {};
    $.ajax('http://the.url.com', {
        type: "GET",
        success: function (res) {
            $(res).each(function (i, v) {
                    var name = v.name;
                    var id = v.id;
                    // create object with building block and tech id to associate techs to BBs
                    myObject[name] = new Array();
                    myObject[name].push(id);
                });
        },
        error: function (xhr) {}
    }
}

Current output:

{
    key1: ["value1c"]
    key2: ["value2a"]
    key3: ["value3b"]
}

Desired output:

{
    key1: ["value1a", "value1b","value1c"]
    key2: ["value2a"]
    key3: ["value3a", "value3b"]
}

How exactly do you match "key1", "key2", "key3"?

GrafiCode
– GrafiCode

2019-03-18 16:12:31 +00:00
Commented Mar 18, 2019 at 16:12 — GrafiCode
– GrafiCode, Commented Mar 18, 2019 at 16:12

mehmetseckin · Accepted Answer · 2019-03-18 16:11:08Z

4

You're overwriting the existing array with a new one for each key, then pushing the latest one in with the following line:

 myObject[name] = new Array();

Try adding a check to avoid overwriting:

 myObject[name] = myObject[name] || new Array();

answered Mar 18, 2019 at 16:11

mehmetseckin

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1 Comment

Jason Over a year ago

Concise. Thanks.

brk · Accepted Answer · 2019-03-18 16:11:25Z

2

The out put is key1: ["value1c"] since key in an object is unique, so it is creating key and storing only latest value. You can use hasOwnProperty and check if myObject has any key by that name. If so then push the value, else create a key value pair and add id to it

$(res).each(function(i, v) {
  var name = v.name;
  var id = v.id;
  if (myObject.hasOwnProperty(name)) {
    myObject[name].push(id);
  } else {
    myObject[name] = [id];
  }
});

answered Mar 18, 2019 at 16:11

brk

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Comments

Serge K. · Accepted Answer · 2019-03-18 16:12:06Z

2

I think that you need to check if myObject[name] already exists before creating a new one. Because if you create a new one each time, it will be overridden

var myFunction = function () {
  var myObject = {};
  $.ajax('http://the.url.com', {
    type: "GET",
    success: function (res) {
      $(res).each(function (i, v) {
        var name = v.name;
        var id = v.id;
        // create object with building block and tech id to associate techs to BBs
        if (!myObject[name]) {
          myObject[name] = new Array();
        }
        myObject[name].push(id);
      });
    },
    error: function (xhr) {}
  }
}

edited Mar 18, 2019 at 16:12

Serge K.

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answered Mar 18, 2019 at 16:10

Hammerbot

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Comments

R3tep · Accepted Answer · 2019-03-18 16:14:45Z

2

You create another array each time with this line :

myObject[name] = new Array();

So you delete the old pushed value each time.

Use a condition to initialize your array if not exist :

!Array.isArray(myObject[name]) && (myObject[name] = new Array());

e.g.

$(res).each(function(i, v) {
      var name = v.name;
      var id = v.id;
      // create object with building block and tech id to associate techs to BBs
      !Array.isArray(myObject[name]) && (myObject[name] = new Array()); 
      myObject[name].push(id);
});

answered Mar 18, 2019 at 16:14

R3tep

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