How to get the value of a variable from a object in JavaScript?

Question

I am having the object config and when I fetch the config["RegionId"], it will give me ${Region}. Now I want to fetch the value of Region. As I have got ${Region}, I thought I could do console.log(`${val}`) to get 'abc'. But it is not working.

How to get this? This is what I have tried,

var config = {
    "RegionId" : "${Region}"
}

var Region = 'abc'
var val = config['RegionId']

console.log(`${val}`)

There's no such thing as a "JSON Object". You just have an object. JSON is a string format. — Scott Marcus, Jul 15 '20 at 15:07
Just remove the quotes around `${Region}` in the object property so that you aren't storing a string, but rather the value of the variable. — Scott Marcus, Jul 15 '20 at 15:08
Hi, @ScottMarcus, actually the configs are stored in a json file. — Abinash Biswal, Jul 15 '20 at 15:14
Fine, but that file holds a JSON "string". There is no such thing as a JSON "object". — Scott Marcus, Jul 15 '20 at 15:15
Yes, @ScottMarcus. Let's say {"key" : "value"}. So the value for a key in any config will be string. So do you have any idea how to get the value? — Abinash Biswal, Jul 15 '20 at 15:17
If you want to convert your JSON string to an object, use `JSON.parse(string)`. I'll update my answer to show this because your question wasn't clear. — Scott Marcus, Jul 15 '20 at 15:19
Actually, you can't store a template literal in a JSON string because they are code and JSON doesn't store code. I'm closing this question as a duplicate. — Scott Marcus, Jul 15 '20 at 15:34

score 3 · Answer 1 · answered Jul 15 '20 at 15:11

Don't put double quotes around the property value. Use back-ticks (for template literal strings) as you are doing for val. And make sure you've declared Region prior to attempting to access it.

var Region = 'abc';

var config = {
    "RegionId" : `${Region}`
};

var val = config['RegionId'];
console.log(`${val}`);

And while your question is centered around template literals, I hope you know that for this scenario, they add no value and are overkill. Here's the same thing with regular strings variables:

var Region = 'abc';

var config = {
    "RegionId" : Region
};

console.log(config['RegionId']);

Rohit · Answer 2 · 2020-07-15T15:31:34.817

-1

try using eval function

var config = {
    "RegionId" : "${Region}"
}

var Region = 'abc'
var val = config['RegionId']


console.log(eval("`"+val+"`"));

edited Jul 15 '20 at 15:31

answered Jul 15 '20 at 15:08

Rohit

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`eval()` is evil and there are really only VERY VERY RARE use cases when it is needed. Most situations that use `eval()` wind up needing it because the solution was not thought out properly. – Scott Marcus Jul 15 '20 at 15:17
This is working. But is there any standard javascript way to do that? I am asking just for knowledge. And how safe is eval? – Abinash Biswal Jul 15 '20 at 15:35
@AbinashBiswal `eval()` is not safe, changes scope, and as my comment above says, should really never be used. This is why `JSON.parse()` was created. It's a safer version of `eval()` for JSON strings, but as I say in my above comment. JSON strings should never contain code, which is what you are doing. You should re-work your thoughts about what you are doing. – Scott Marcus Jul 15 '20 at 15:41

How to get the value of a variable from a object in JavaScript?

2 Answers2