Updating documents of mongodb using react nodejs and ajax

If you go to the react website, and look at their tutorial they have a great example of a ajax call done.

Basically you write your ajax function first so it might look something like this if it is a GET request :

your nodejs code:

//the route we get our users at is allUsers
app.get('/allUsers, function(req, res) { 
User.find({}, function(err, userarray) { //we grab all users from our mongo collection, and that array of users is called userarray
      res.json(userarray); //we return the json with it
  });
});

Now for the react part:

var Users = React.createClass({

getUsers : function() { //we define a function for getting our users

   $.ajax({ //call ajax like we would in jquery
            url: '/allUsers',  //this is the url/route we stored our users on
            dataType: 'json',
            success: function(data) { //if we get a Success for our http get then..
               this.setState({user:data}); //set the state of our user array to whatever the url returned, in this case the json with all our users
               }.bind(this),
        error: function(xhr, status, err) { //error logging and err tells us some idea what to debug if something went wrong.
                console.log("error");
               console.error(this.props.url,status, err.toString());
            }.bind(this)
        });

   },

getInitialState: function() { //setting our initial state for our user array we want to use in our react code
       return {

          users: [], //initialize it empty, or with whatever you want

       }
    },

componentDidMount : function() {
this.getUsers(); //we are invoking our getUsers function here, therefore performing the ajax call
},

render : function() {
return(
//do what we want to do with our array here I guess!
<div>

<PrintArray users = {this.state.users} />

</div>
)
}
});
//Our new Class called Printarray
var PrintArray = React.createClass({
render : function() {
    //Psuedocode
    return(
     ul {
       this.props.users.map(function(user){  //we are mapping all our users to a list, this.props.users is inheritance what we passed down from our Users class
            return (
            <li key = user.id> user.name </li>
            )
      })

     )
}
    </ul>
});

And then finally just call our main class,

React.render(<Users   />,
document.getElementById(domnNode)); //your div's id goes here

I commented out the code, if you have anymore questions feel free to ask! I don't know if you wanted to do a post method either, but its similar. You just change the GET to a POST, and instead of the function having no parameters, you most likely want a parameter for it, so it might be something like :

sendNewUser : function(data) {
 //do ajax post stuff here
}

and in render:

render : function(){
   sendNewUser(blah);
}

except you would probably have a form or something or even another class that deals with adding a new user. The question seemed really broad so I just gave a general overview of how I would do it!