How do you create Object of Arrays in Javascript

Question

I spent more time on this than I would like to admit. I have trouble constructing an object filled with an array.

I would like my data to look like this:

items={
    {
     '2012-05-22': [{text: 'item 1 - any js object'}],
     '2012-05-23': [{text: 'item 2 - any js object'}],
     '2012-05-24': [],
     '2012-05-25': [{text: 'item 3 - any js object'},{text: 'any js object'}],
    }
}

I am making a database call and the data I receive looks like this:

Object {start: "08:00:00", end: "09:00:00", full_name: "Tomomi", date: "2017-06-08", Barber_id: "1"…}

The data I am interested in is the full_name value and the date value.

This is what I have attempted:

let  newItems = {};
axios.post(endpoint, {lookup: day.dateString}).then((customerData) => {
    customerData.data.forEach((val,key)=>{
        newItems = {[val.date]:[]};
        newItems[val.date].push({name:val.full_name});
        console.log(newItems); 
    })
}

It looks like this:

Object {2017-06-08: Array(1)}
2017-06-08
:
Array(1)

This is very close, but the problem is that my code is overwriting my data. I am trying to create this dynamically:

'2012-05-25': [{text: 'item 3 - any js object'},{text: 'any js object'}],

So that each date can have many users. Hopefully, this makes sense.

Thanks for any help.

How do you call .forEach() on an object without an error? What is customerData.data, an array or an object? — guest271314
– guest271314, Commented Jun 9, 2017 at 20:19
Also, from the result you're looking for - seems you're not actually interested at all in full_name — Roko C. Buljan
– Roko C. Buljan, Commented Jun 9, 2017 at 20:19
I am trying to push the value of the customer into the object. with this line:newItems[val.date].push({name:val.full_name}) — Louis345
– Louis345, Commented Jun 9, 2017 at 20:25

Peter Schweitzer Jr · Accepted Answer · 2017-06-09 20:39:47Z

2

The function expression you pass to forEach has this as the first line:

newItems = {[val.date]:[]};

This resets the newItems object to an object with one date:name pair. You really want something more like:

newItems[val.date]?newItems[val.date].push({name:val.full_name}):newItems[val.date]=[];

answered Jun 9, 2017 at 20:39

Peter Schweitzer Jr

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1 Comment

Louis345 Over a year ago

This was very helpful. Thank you.

Roko C. Buljan · Accepted Answer · 2017-06-09 20:48:20Z

1

var byDate = {}; // Object to store received data by-date

function addIntoByDate( obj ) {
  byDate[obj.date] = byDate[obj.date] || [];
  byDate[obj.date].push( obj );
}

// Simulate adding server data one by one
addIntoByDate( {date: "2017-06-08", full_name: "Cat", text:"Foo!!"}  ); // < SAME DATE
addIntoByDate( {date: "2016-05-23", full_name: "Dog", text:"Bar"}    );
addIntoByDate( {date: "2017-06-08", full_name: "Bug", text:"Baz..."} ); // < SAME DATE

// test
console.dir(byDate);

edited Jun 9, 2017 at 20:48

answered Jun 9, 2017 at 20:35

Roko C. Buljan

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Comments

guest271314 · Accepted Answer · 2017-06-09 20:35:18Z

1

You can use object destructuring, computed property and Object.assign()

const newItems = {};

const data = [
               {
                 start: "08:00:00"
               , end: "09:00:00"
               , full_name: "Tomomi"
               , date: "2017-06-08"
               , Barber_id: "1"
               }
             ];

data.forEach(({date, full_name}) => 
  Object.assign(newItems, {[date]: [{/* text: */ full_name}]}));
  
console.log(newItems);

answered Jun 9, 2017 at 20:35

guest271314

1

1 Comment

Louis345 Over a year ago

I totally forgot about Object.assign this was helpful, but Roko's answer worked a bit better for me.

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