how can I use data posted from ajax in flask?

Question

I'm having trouble getting data POSTed from jquery ajax.

$('#clickme').click( function() {
    var data = save_input(); // data

    data['_sid'] = $survey_id;  // survey_id injected from flask
    data['_uip'] = $user_ip; // user_ip injected from flask, request.remote_addr

    $.ajax({
        type : "POST",
        url : "{{ url_for('mod.load_ajax') }}",
        data: JSON.stringify(data),
        contentType: 'application/json;charset=UTF-8',
        success: function(result) {
            console.log(result);
        }
    });

    console.log(data);
});

from the code, data is a javascript object like

{
    'foo' : 'foo',
    'bar' : 'bar',
    'fo_' : 42,
}

what I'm trying to do in flask is :

@mod.route('/load_ajax', methods=["GET", "POST"])
def load_ajax():
    if request.method == "POST":
        # load _sid and _uip from posted JSON and save other data
        # but request.form is empty.
        # >>> request.form
        # ImmutableMultiDict([]) 
        return str(request.form)

see, the ajax request is made but no data is submitted. I do console.log(data) with ajax so I can see that I really have some meaningful data in data variable in jquery. but request.form in ajax view is empty. Where is my data submitted?

Solution 1

Try

 $.ajax({
    type : "POST",
    url : "{{ url_for('mod.load_ajax') }}",
    data: JSON.stringify(data, null, '\t'),
    contentType: 'application/json;charset=UTF-8',
    success: function(result) {
        console.log(result);
    }
});

Then from the server, you can refer to the variables in data like this :

request.json['foo']

Since the content type is specified as application/json the data is in request.json

Solution 2

As per your example you are not sending a key value pair but rather assigning a JSON string to the jQuery data option. As mentioned in the comments you have to stringify your JSON, create an object with a key (which will be used to access the JSON string from flask) and then assign it to the jQuery data key.

    $.ajax({
            type : "POST",
            url : "{{ url_for('mod.load_ajax') }}",
            data: {json_str: JSON.stringify(data)},
            contentType: 'application/json;charset=UTF-8',
            success: function(result) {
                console.log(result);
            }
        });

    @mod.route('/load_ajax', methods=["GET", "POST"])
    def load_ajax():
        if request.method == "POST":
            # load _sid and _uip from posted JSON and save other data
            # but request.form is empty.
            # >>> request.form
            # ImmutableMultiDict([]) 
            return str(request.form['json_str']
     )

Solution 3

On the flask side, use:

data = request.get_json()

The variable data now has the dictionary you sent using ajax and you can now manipulate it with python

Solution 4

Have you tried remove contentType? You suppose to post data to Flask.

could you try add fake data like

data:{"hello":"world"} inside ajax? just to check if the hello world arrive to request.form

View more solutions

Comments

[Blender]

Change JSON.stringify(data) to data and see what happens.

[thkang]

@Blender I do recieve the data. How can I receive this in JSON format?

[Blender]

Have you tried request.json?

[11684]

@thkang use this as Data string: "data=" + JSON.stringify(data);.

[Simon Melouah]

Was pulling my hair out looking for this, request.json['foo'] did it for me. Thanks :)

[akai]

charset=UTF-8 was the trick. I was looking for it for hours.

[Dee]

yes, Flask request.data is empty when having no contentType in jquery ajax settings

[Divij Sehgal]

Wrote that code after staying up for 24+ hours straight. Missed a few things. I take it back. It works perfectly. My bad.