Automatically set a JWT if the current one is invalid

CheckAndSetAnAuthToken.js

// This can be placed in the Pre-requests on the collection level.
// It will check to see if certain valid variables are present in an environment file.
// If these are not present, it be go and get another valid token
// The 'AuthData' variable is a Base64 encoded client_id and client_secret
// This my need to be tweaked for your needs but the mechanism will work.

const moment = require('moment')

const getJWT = {
    url: `${pm.environment.get('tokenBaseURL')}/Auth/connect/token`,
    method: 'POST',
    header: {
        'Content-Type': 'application/x-www-form-urlencoded',
        'Authorization': `Basic ${pm.environment.get('AuthData')}`
    },
    body: {
        mode: 'urlencoded',
        urlencoded: [
            {key: 'grant_type', value: 'client_credentials'},
            {key: 'scope', value: '<scope details>'}
        ]
    }
}

var getToken = true

if (!_.has(pm.environment.toObject(), 'AccessTokenExpiry') 
    || !_.has(pm.environment.toObject(), 'jwt')
    || pm.environment.get('AccessTokenExpiry') <= moment().valueOf()) {
} else {
    getToken = false
}

if (getToken) {
    pm.sendRequest(getJWT, (err, res) => {
        if (err === null) {
            pm.environment.set('jwt', `Bearer ${res.json().access_token}`)
            
            var expiryDate = moment().add(res.json().expires_in, 's').valueOf()
            pm.environment.set('AccessTokenExpiry', expiryDate)
        }
    })
}