Javascript puts the variable name as it is inside a json and not its value

manpreet Best Answer 2 years ago

I observed a very weird phenomena in javascript and I can't figure out why. Consider this example below

state = "West Bengal"
city = "Kolkata"
country = "India"
some_json = {country: {"city": city, "state": state, "col_val": {}}}
console.log(some_json)

When I do a console.log() of some_json variable, I get this below

{ country: { city: 'Kolkata', state: 'West Bengal', col_val: {} } }

As you can see it replaced every other variable's values with the one defined above except country. Why is that?

When I perform the same operation in Python, it works just fine.

state = "West Bengal"
city = "Kolkata"
country = "India"
some_json = {country: {"city": city, "state": state, "col_val": {}}}

print(some_json)

Here doing a print gives me the expected outcome

{'India': {'state': 'West Bengal', 'col_val': {}, 'city': 'Kolkata'}}

So why is it giving different outcome in javascript? How can I fix this since I need to work with this exact format?

manpreet 2 years ago

When using a variable as key of an object in javascript use square bracket

let state = "West Bengal"
let city = "Kolkata"
let country = "India"
some_json = {
  [country]: {
    "city": city,
    "state": state,
    "col_val": {}
  }
}
console.log(some_json)

manpreet 2 years ago

You need to make country a dynamic property name with []:

var state = "West Bengal",
  city = "Kolkata",
  country = "India",
  some_json = {
    [country]: {
      "city": city,
      "state": state,
      "col_val": {}
    }
  };
console.log(some_json);

manpreet 2 years ago

use it like this, and it will work

state = "West Bengal"
city = "Kolkata"
country = "India"
some_json = {}
some_json[country] = {"city": city, "state": state, "col_val": {}}
console.log(some_json)

manpreet 2 years ago

As you said it's working in python, Python will consider it as directory not as JSON object.

In JavaScript, by default it replaces only value part of JSON with variable. It won't consider key to be replaced with variable value.

To force JavaScript to consider key and replace it with variable value, you have to tell to JavaScript explicitly by using []. Try below code:

state = "West Bengal"
city = "Kolkata"
country = "India"
some_json = {[country]: {"city": city, "state": state, "col_val": {}}}
console.log(some_json)