How to get Microsoft Graph API Access token from Node Script?

BU0's answer didn't work correctly for me because Microsoft changed their way of using the graph API so I wasn't able to get all the data I needed. Here's how I did it using BU0 answer and this tutorial:

const request = require("request");

const endpoint = "https://login.microsoftonline.com/[Tenant]/oauth2/v2.0/token";
const requestParams = {
    grant_type: "client_credentials",
    client_id: "[ApplicationID]",
    client_secret: "[Key]",
    scope: "https://graph.microsoft.com/.default"
};

request.post({ url: endpoint, form: requestParams }, function (err, response, body) {
    if (err) {
        console.log("error");
    }
    else {
        console.log("Body=" + body);
        let parsedBody = JSON.parse(body);
        if (parsedBody.error_description) {
            console.log("Error=" + parsedBody.error_description);
        }
        else {
            console.log("Access Token=" + parsedBody.access_token);
        }
    }
});

function testGraphAPI(accessToken) {
    request.get({
        url:"https://graph.microsoft.com/v1.0/users",
        headers: {
          "Authorization": "Bearer " + accessToken
        }
    }, function(err, response, body) {
        console.log(body);
    });
}

To run a back-end non-user-authenticated daemon connected to the Graph API, you want to use the app-only authentication flow. Here's a quick summary of the official steps:

1. Create your Azure AD Tenant. Note the yourtenant.onmicrosoft.com name, and copy this value down.
2. Register an application through the global Azure Active Directory blade's App Registrations section, not directly within the tenant properties. Copy the Application ID; we'll need it later.
3. Create a key tied to the registration and remember to copy it down. Once you click out, you can't get the key value back, so make sure to copy it.
4. Also update the registration's permissions to what you need, click Save, and then also hit the Grant Permissions button.
5. Make an HTTP request to the login.microsoftonline.com domain to obtain an access token.
6. Use the access token to make Graph API requests.

Here's a link to Microsofts Node.js example, and here's a link to the direct documentation on the HTTP call to make to retrieve an access token. And here's a super stripped-down example that will output the retrieved access token. Replace the [Tenant], [ApplicationID], and [Key] values:

const request = require("request");

const endpoint = "https://login.microsoftonline.com/[Tenant].onmicrosoft.com/oauth2/token";
const requestParams = {
    grant_type: "client_credentials",
    client_id: "[ApplicationID]",
    client_secret: "[Key]",
    resource: "https://graph.windows.net"
};

request.post({ url:endpoint, form: requestParams }, function (err, response, body) {
    if (err) {
        console.log("error");
    }
    else {
        console.log("Body=" + body);
        let parsedBody = JSON.parse(body);         
        if (parsedBody.error_description) {
            console.log("Error=" + parsedBody.error_description);
        }
        else {
            console.log("Access Token=" + parsedBody.access_token);
        }
    }
});

Once we have the access_token, we can call out to the Graph API. Assuming the apps permissions were configured correctly and applied from step #4, we can start making Graph API requests:

function testGraphAPI(accessToken) {
    request.get({
        url:"https://graph.windows.net/[Tenant]/users?api-version=1.6",
        headers: {
          "Authorization": accessToken
        }
    }, function(err, response, body) {
        console.log(body);
    });
}