Appending to an object

I have an object that holds alerts and some information about them:

var alerts = { 
    1: { app: 'helloworld', message: 'message' },
    2: { app: 'helloagain', message: 'another message' }
}

In addition to this, I have a variable that says how many alerts there are, alertNo. My question is, when I go to add a new alert, is there a way to append the alert onto the alerts object?

How about storing the alerts as records in an array instead of properties of a single object ?

var alerts = [     {num : 1, app:'helloworld',message:'message'},    {num : 2, app:'helloagain',message:'another message'} ]

And then to add one, just use push:

alerts.push({num : 3, app:'helloagain_again',message:'yet another message'});

jQuery $.extend(obj1, obj2) would merge 2 objects for you, but you should really be using an array.

var alertsObj = {
    1: {app:'helloworld','message'},
    2: {app:'helloagain',message:'another message'}
};

var alertArr = [    {app:'helloworld','message'},    {app:'helloagain',message:'another message'}];

var newAlert = {app:'new',message:'message'};

$.extend(alertsObj, newAlert);
alertArr.push(newAlert);

You can do this with Object.assign(). Sometimes you need an array, but when working with functions that expect a single JSON object -- such as an OData call -- I've found this method simpler than creating an array only to unpack it.

var alerts = { 
    1: {app:'helloworld',message:'message'},
    2: {app:'helloagain',message:'another message'}
}

alerts = Object.assign({3: {app:'helloagain_again',message:'yet another message'}}, alerts)

//Result:
console.log(alerts)
{ 
    1: {app:'helloworld',message:'message'},
    2: {app:'helloagain',message:'another message'}
    3: {app: "helloagain_again",message: "yet another message"}
} 

EDIT: To address the comment regarding getting the next key, you can get an array of the keys with the Object.keys() function -- see Vadi's answer for an example of incrementing the key. Similarly, you can get all the values with Object.values() and key-values pairs with Object.entries().

var alerts = { 
    1: {app:'helloworld',message:'message'},
    2: {app:'helloagain',message:'another message'}
}
console.log(Object.keys(alerts))
// Output
Array [ "1", "2" ]

You can use spread syntax as follows..

var alerts = { 
1: { app: 'helloworld', message: 'message' },
2: { app: 'helloagain', message: 'another message' }
 }

alerts = {...alerts, 3: {app: 'hey there', message: 'another message'} }

Now with ES6 we have a very powerful spread operator (...Object) which can make this job very easy. It can be done as follows:

let alerts = { 
   1: { app: 'helloworld', message: 'message' },
   2: { app: 'helloagain', message: 'another message' }
} 

//now suppose you want to add another key called alertNo. with value 2 in the alerts object. 
 
alerts = {
   ...alerts,
   alertNo: 2
 }

Thats it. It will add the key you want. Hope this helps!!

Like other answers pointed out, you might find it easier to work with an array.

If not:

var alerts = { 
    1: {app:'helloworld',message:'message'},
    2: {app:'helloagain',message:'another message'}
}

// Get the current size of the object
size = Object.keys(alerts).length

//add a new alert 
alerts[size + 1] = {app:'Your new app', message:'your new message'}

//Result:
console.log(alerts)
{ 
    1: {app:'helloworld',message:'message'},
    2: {app:'helloagain',message:'another message'}
    3: {app: "Another hello",message: "Another message"}
}      

try it:

https://jsbin.com/yogimo/edit?js,console

You should really go with the array of alerts suggestions, but otherwise adding to the object you mentioned would look like this:

alerts[3]={"app":"goodbyeworld","message":"cya"};

But since you shouldn't use literal numbers as names quote everything and go with

alerts['3']={"app":"goodbyeworld","message":"cya"};

or you can make it an array of objects.

Accessing it looks like

alerts['1'].app
=> "helloworld"

Do you have the ability to change the outer-most structure to an array? So it would look like this

var alerts = [{"app":"helloworld","message":null},{"app":"helloagain","message":"another message"}];

So when you needed to add one, you can just push it onto the array

alerts.push( {"app":"goodbyeworld","message":"cya"} );

Then you have a built-in zero-based index for how the errors are enumerated.

Way easier with ES6:

let exampleObj = {
  arg1: {
    subArg1: 1,
    subArg2: 2,
  },
  arg2: {
    subArg1: 1,
    subArg2: 2,
  }
};

exampleObj.arg3 = {
  subArg1: 1,
  subArg2: 2,
};

console.log(exampleObj);

{
arg1: {subArg1: 1, subArg2: 2}
arg2: {subArg1: 1, subArg2: 2}
arg3: {subArg1: 1, subArg2: 2}
}

As an alternative, in ES6, spread syntax might be used. ${Object.keys(alerts).length + 1} returns next id for alert.

let alerts = { 
    1: {app:'helloworld',message:'message'},
    2: {app:'helloagain',message:'another message'}
};

alerts = {
  ...alerts, 
  [`${Object.keys(alerts).length + 1}`]: 
  { 
    app: `helloagain${Object.keys(alerts).length + 1}`,message: 'next message' 
  } 
};

console.log(alerts);

I'm sorry but i can't comment your answers already due my reputation!...so, if you wanna modify the structure of your object, you must do like Thane Plummer says, but a little trick if you do not care where to put the item: it will be inserted on first position if you don't specify the number for the insertion.

This is wonderful if you want to pass a Json object for instance to a mongoDB function call and insert a new key inside the conditions you receive. In this case I gonna insert a item myUid with some info from a variable inside my code:

// From backend or anywhere
let myUid = { _id: 'userid128344'};
// ..
// ..

  let myrequest = { _id: '5d8c94a9f629620ea54ccaea'};
  const answer = findWithUid( myrequest).exec();

// ..
// ..

function findWithUid( conditions) {
  const cond_uid = Object.assign({uid: myUid}, conditions);
  // the object cond_uid now is:
  // {uid: 'userid128344', _id: '5d8c94a9f629620ea54ccaea'}
  // so you can pass the new object Json completly with the new key
  return myModel.find(cond_uid).exec();
}

[Javascript] After a bit of jiggery pokery, this worked for me:

 let dateEvents = (
            {
                'Count': 2,
                'Items': [
                    {
                        'LastPostedDateTime': {
                            "S": "10/16/2019 11:04:59"
                        }
                    },
                    {
                        'LastPostedDateTime': {
                            "S": "10/30/2019 21:41:39"
                        }
                    }
                ],
            }
        );
        console.log('dateEvents', dateEvents);

The problem I needed to solve was that I might have any number of events and they would all have the same name: LastPostedDateTime all that is different is the date and time.

Try this:

alerts.splice(0,0,{"app":"goodbyeworld","message":"cya"});

Works pretty well, it'll add it to the start of the array.