Postman-Azure-Active-Directory-Bearer-Token-Pre-Request-Script.js

pm.sendRequest({
        url: 'https://login.microsoftonline.com/' + pm.environment.get("tenantId") + '/oauth2/token',
        method: 'POST',
        header: 'Content-Type: application/x-www-form-urlencoded',
        body: {
            mode: 'urlencoded',
            urlencoded: [ 
                {key: "grant_type", value: "client_credentials", disabled: false},
                {key: "client_id", value: pm.environment.get("clientId"), disabled: false},
                {key: "client_secret", value: pm.environment.get("clientSecret"), disabled: false},
                {key: "resource", value: pm.environment.get("resource"), disabled: false}
            ]
        }
    }, function (err, res) {
        pm.globals.set("bearerToken", res.json().access_token);
        console.log(pm.globals.get("bearerToken"));
    });

credit to https://blog.jongallant.com/2019/04/azure-rest-apis-postman-in-no-time-flat/