How to add a loop variable to the callback of an asynchronous request?

Question

JavaScript

How to use the key variable in the callback if by the time the first handler is run, key=last key.
I tried to save to a temporary variable inside the loop - it did not help.
It's an option to pass key as a function argument, but how do you do that in the npm request module?

for(var key in reqObj) {
  request(options, (err, res, body) => {
    if (!err && res.statusCode == 200) {
       resultObj[key] = body;
    }
    ....
  });
}

Answer 1

for(var key in reqObj) {
(function(key){
  request(options, (err, res, body) => {
    if (!err && res.statusCode == 200) {
       resultObj[key] = body;
    }
    ....
  });
})(key)
}

Answer 2

Through a promise

for(var key in reqObj) {
    new Promise(function(resolve, reject) {
        var k = key;
            request(options, (err, res, body) => {
            if (!err && res.statusCode == 200) {
                resultObj[k] = body;
            }
        ....
        });
    });
}