Postman Prerequest Script to store an auth token before each API request

postman_prereq_auth.js

// we use this to set an expiry on the token
var currTime = new Date().getTime();
// If there is an expiry value and it's before current time then we've expired
if (pm.globals.get("tokenExpiry") !== '' && pm.globals.get("tokenExpiry") <= currTime){
    console.log('Token Expiry Exceeded. Clearing token');
    pm.globals.set("token",'')
}
// If we have a valid token then we don't need to request it we'll reuse it
if (pm.globals.get("token") !== ''){
    console.log("Auth Token. Set So Not logging in again");
} else {
    // send request to auth
    pm.sendRequest({
        url: 'http://' + pm.variables.get("host") + '/api/login',
        method: 'POST',
        header: {
            'content-type': 'application/json'
        },
        body: {
            mode: 'raw',
            raw: JSON.stringify({
                	userName:  pm.variables.get("username"),
	                password: pm.variables.get("password") })
        }
    }, function (err, res) {
       if (err) { console.log(err);
       console.log('res : ' + res);
         
       }
       else{
         // if it's a 401 then we can clear the token and expiry out
         // although really this should maybe be in the 'test' section after the main request as
         // it's that 401 we would care more about
           if (res.code === 401) {
               console.log('clearing token');
               pm.globals.set("token",'');
               pm.globals.unset("tokenExpiry");

           }else {
             // set the token
            pm.globals.set("token",res.json().token.mintedToken);
             // set the expiry for 30 seconds from the start of this request
            pm.globals.set("tokenExpiry",(currTime + 30000));
        }

       }
    });
}