Stop copying & pasting the response key value to your variable, and let's automate this action using the coming marvelous way with considering that you are returning a response similar to the below schema:

{
    "key": "success",
    "msg": "You have logged in successfully",
    "data": {
        "name": "Mahmoud Ramadan",
        "token": "1|7XJ3hr2HZmQD24D9fkKYrmPB6ivCo7b9imbUP7NA"
    }
}

At first, I will hypothesize that you have defined a `token` variable as a Global scope. Postman has multiple tabs under the URL input, especially the Tests tab, go ahead and open it, then write the next JavaScript code:

var response = JSON.parse(responseBody);

pm.globals.set("token", response.data.token);

There are two ways to run these scripts, I have already mentioned one way which is the `Tests` tab in addition, you can use the `Pre-request Script` tab to run scripts before dispatching the requests.

We can not run the former script in the `Pre-request Script` tab that's because, before dispatching the request Postman will search for the `data` key object and will not find it, so it will fire an error.

Now, let's look at that variable after you have sent the request. Boom..the value has been populated 🚀

Hmm..I think that we often deal with Postman Collections so, let's do so and create the `token` variable in your Collection then choose an endpoint that you need, and at last write the following code:

var response = JSON.parse(responseBody);

pm.collectionVariables.set("token", response.data.token);

Then, if you dispatch the request again, you will find that the variable has been filled again!

To dive into the many ways of defining the variables in Postman, I recommend reading that Article.

To evade any errors, you can check whether the response contains a `data` object or not, because we may not receive a response for some reason, to avoid Postman from triggering an error about missing that key:

var response = JSON.parse(responseBody);

if (response.data !== undefined && response.data.token !== undefined) {
    pm.collectionVariables.set("token", response.data.token);
}