Simple:

var data = [{"name":"Marine Lines","location_id":3},{"name":"Ghatkopar","location_id":2}]
var result = data.map(function(val) {
  return val.location_id;
}).join(',');

console.log(result)

I assume you wanted a string, hence the .join(','), if you want an array simply remove that part.

This can be achieved via the join() method which is built into the Array type:

const object = {
"id" : "122223232244",
"title" : "התרעת פיקוד העורף",
"data" : ["עוטף עזה 218","עוטף עזה 217"]
}

/* Join elements of data array in object to a comma separated string */
const value = object.data.join();

console.log(value);

If no separator argument is supplied, then the join() method will default to use a comma separator by default.

Update

If the JSON was supplied in raw text via a string you can use the JSON.parse() method to extract an object from the JSON string value as a first step like so:

const json = `{"id" : "122223232244","title" : "התרעת פיקוד העורף","data" : ["עוטף עזה 218","עוטף עזה 217"]}`

/* Parse input JSON string */
const object = JSON.parse(json);

/* Join elements of data array in object to a comma separated string */
const value = object.data.join();

console.log(value);

You can do the following,

data = [
  {'id': 1,
  'name': 'book',
  'colors': 'red, yellow, blue'
  },
  {'id': 2,
  'name': 'book',
  'colors': 'red, yellow, blue'
  }
 ];
 
 ret = data.map((item) => {
   return {...item, colors: item.colors.split(',').map(item => item.trim())};
 })

console.log(ret);

Just adding all the steps:-

1). Taking your JSON in a variable.

data = {"url":"http://example.com/main.aspx","report_template_id":"1","interval_secs":"86400","analysis_type":"lite","email":"[email protected]","alerts":["num_domains","med_load_time","avg_load_time","tot_req"]};

2). Parse JSON data to object. Assuming the JSON is a string initially do a typeof(data) to be clear.

data = JSON.parse(data);

3) Change list of alerts to comma separated values

data.alerts = data.alerts.join(',');

4) Convert back to string

data = JSON.stringify(data)

So data will look like

{
    "url": "http://example.com/main.aspx",
    "report_template_id": "1",
    "interval_secs": "86400",
    "analysis_type": "lite",
    "email": "[email protected]",
    "alerts": "num_domains,med_load_time,avg_load_time,tot_req"
}

Note:- If you will just say join() then also it will work, because default delimiter is , only, just to clarify I have given that.

var json = [];
var to = '[email protected],[email protected],[email protected]';
var toSplit = to.split(",");
for (var i = 0; i < toSplit.length; i++) {
    json.push({"email":toSplit[i]});
}

Push each value into an array and then use .join() to make a comma-delimited string.

const response = {
  chartstatus: [{
      abs_status: "Bekerja",
      total: "12"
    },
    {
      abs_status: "Tanpa Keterangan",
      total: "5"
    },
    {
      abs_status: "Hari Libur",
      total: "1"
    }
  ]
}

let nama_status = [];
let jumlah = [];

$.each(response.chartstatus, function(key, value) {
  status = value.abs_status.toString();
  nama_status.push('"' + status + '"');
  jumlah.push(value.total)

});
console.log(nama_status.join(', ')); 
console.log(jumlah.join(', '));

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

This will convert it into an array (which is the JSON representation you specified):

var array = myString.split(',');

If you need the string version:

var string = JSON.stringify(array);

The method array.toString() actually calls array.join() which result in a string concatenated by commas. ref

var array = ['a','b','c','d','e','f'];
document.write(array.toString()); // "a,b,c,d,e,f"

Also, you can implicitly call Array.toString() by making javascript coerce the Array to an string, like:

//will implicitly call array.toString()
str = ""+array;
str = `${array}`;

Array.prototype.join()

The join() method joins all elements of an array into a string.

Arguments:

It accepts a separator as argument, but the default is already a comma ,

str = arr.join([separator = ','])

Examples:

var array = ['A', 'B', 'C'];
var myVar1 = array.join();      // 'A,B,C'
var myVar2 = array.join(', ');  // 'A, B, C'
var myVar3 = array.join(' + '); // 'A + B + C'
var myVar4 = array.join('');    // 'ABC'

Note:

If any element of the array is undefined or null , it is treated as an empty string.

Browser support:

It is available pretty much everywhere today, since IE 5.5 (1999~2000).

References

• ECMA Specification
• Mozilla
• MSDN

You can use join

let arr = ["Varberg","Halmstad","Falkenberg"]

console.log(arr.join(','))

You need to parse the string you get from the sessionStorage, then you can map and join:

var profile = '{"domiciles":[{"country":"AF"},{"country":"AX"},{"country":"AL"}],"investor":[{"type":"ii"},{"type":"pi"}]}'; // sessionStorage.getItem("profile");

var dataResidence = JSON.parse(profile);

function mapAndJoin(arr, key) {
  return arr.map(function(o) {
    return o[key];
  }).join();
}

var domiciles = mapAndJoin(dataResidence.domiciles, 'country');

var investor = mapAndJoin(dataResidence.investor, 'type');

console.log(domiciles);

console.log(investor);