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);

Since the string (including its double quotes) seems to be a properly formatted JSON string, we could pass it, as JSON, to the JSON processor jq and split it on the commas:

$ echo '"3.8,3.9,3.10"' | jq 'split(",")'
[
  "3.8",
  "3.9",
  "3.10"
]

Use jq with -c to get "compact output":

$ echo '"3.8,3.9,3.10"' | jq -c 'split(",")'
["3.8","3.9","3.10"]

Giving it to an internal jq variable on the command line and then splitting that variable's value:

$ jq -c -n --argjson str '"3.8,3.9,3.10"' '$str|split(",")'
["3.8","3.9","3.10"]

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.

You can use REPLACE to get the expected string:

SELECT CONCAT('["', REPLACE('technician,director,website designer', ',', '","'), '"]')
-- ["technician","director","website designer"]

Using JSON_VALID you can check if the result of the conversion is a valid JSON value:

SELECT JSON_VALID(CONCAT('["', REPLACE('technician,director,website designer', ',', '","'), '"]'))
-- 1

demo on dbfiddle.uk

Considering you use a Json.net library, I suggest first to split your string to an array by comma andserialize it to a string:

var ids = "100,140".Split(',');
var personsString = JsonConvert.SerializeObject(new { person = ids.Select(x => new { id = x }).ToList()});

In my example, i serialize a dynamic type, but you can implement your custom class Person with ids array.

For such a trivial example, it's pretty easy to produce a poorly-formed JSON String of your content and let JSONObject patch it up.

In a single expression:

new JSONObject(String.format("{%s}", str.replaceAll("([^,]+),([^,]+)(,|$)", "$1:$2,")))
// {"art":0,"comedy":0,"action":0,"crime":0,"animals":0}

If you really want to keep the 0.0 as Strings:

new JSONObject(String.format("{%s}", str.replaceAll("([^,]+),([^,]+)(,|$)", "$1:\"$2\",")))
// {"art":"0.0","comedy":"0.0","action":"0.0","crime":"0.0","animals":"0.0"}

If you want to account for possible extraneous whitespaces:

new JSONObject(String.format("{%s}", str.replaceAll("([^,]+)\\s*?,\\s*?([^,]+)(,|$)", "$1:$2,")))

.. will work with inputs like "art, 0.0, comedy, 0.0, action, 0.0, crime, 0.0, animals, 0.0" and other cases.

Disclaimer: it's not crazy-sexy code but drop in a one-line comment and it could be reasonable so long as the data structure stays simplistic.

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);

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);

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]});
}