Load Bearer token on each postman request

pre-request.js

//add this as pre-request script on postman collection
const moment = require("moment")
const {
    apiRoot,
    authPath,
    username,
    password,
    bearerTokenValidUntil
} = pm.variables.toObject();

const req = {
    url: apiRoot + "/" + authPath,
    method: "POST",
    header: {
        'Content-Type': 'application/x-www-form-urlencoded'
    },
    body: {
        mode: "urlencoded",
        urlencoded: [
            {key: "grant_type", value: "password"},
            {key: "username", value: username},
            {key: "password", value: password}
        ]
    }
}
const resHandler = (err, res) => {
    const {access_token, ".expires" : expires} = res.json()
    pm.environment.set("bearerToken", access_token);
    pm.environment.set("bearerTokenValidUntil", expires);
}

if (!bearerTokenValidUntil || moment(bearerTokenValidUntil).isBefore(moment())) {
    pm.sendRequest(req, resHandler);
}