Ajax and Django and jQuery - .attr()

[Jan Gregorczyk]

I have a problem with Ajax and Django templates. I'm new to Ajax and jquery.

Console log at the end of the script prints undefined. I don't know why let answerid = $(this).attr("answer-id"); doesn't extract attribute from this line: <i class="upvote" answer-id="{{answer.id}}">&#8593</i>

I also want to know if using template tags in javascript scripts like here $.post("{% url 'upvote' %}", {answer_id:answerid}) is a good idea.

{% extends 'base.html' %}

{% block title %}{{question.title|truncatechars:52}}{% endblock %}

{% block content %}

<h1>{{question.title}}</h1>

<p>{{question.content}}</p>

{% for answer in question.answers.all %}

<h3>{{answer.author}}</h3>

<p>{{answer.content}}</p>

<p>

<i class="upvote" answer-id="{{answer.id}}">&#8593</i>

{{answer.votes.count}}

<i class="downvote" answer-id="{{answer.id}}">&#8595</i>

</p>

{% endfor %}

<form method="POST" action="{% url 'answer' question.id %}">

{% csrf_token %}

{{form.as_p}}

<input type="submit" value="Odpowiedz">

</form>

{% endblock %}

{% block javascript %}

{% load static %}

<script src="https://cdn.jsdelivr.net/npm/js-cookie@rc/dist/js.cookie.min.js"></script>

<script>

//upvote and downvote script

var csrftoken = window.Cookies.get('csrftoken');

function csrfSafeMethod(method) {

// these HTTP methods do not require CSRF protection

return (/^(GET|HEAD|OPTIONS|TRACE)$/.test(method));

}

$.ajaxSetup({

beforeSend: function(xhr, settings) {

if (!csrfSafeMethod(settings.type) && !this.crossDomain) {

xhr.setRequestHeader("X-CSRFToken", csrftoken);

}

}

});

$(".upvote").click( () => {

let answerid = $(this).attr("answer-id");

console.log(answerid);

$.post("{% url 'upvote' %}", {answer_id:answerid});

});

</script>

{% endblock %}

[Stephen J. Butler]

This isn't a jQuery issue, it's a JavaScript/ECMAScript issue. When you use the "arrow function" style like "() => { ...code... }" then certain variables are not bound into the function contact, including "this". https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

To get "this" inside your event handler you need to use "function () { code... }".

$(".upvote").click( function () {

            let answerid = $(this).attr("answer-id");
            console.log(answerid);
            $.post("{% url 'upvote' %}", {answer_id:answerid});
});

But also, it's bad bad form to define your own attribute names on HTML. Use the "data-answer-id" attribute name to do this, and in your code access it with $(this).data("answer-id").

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[mel...@melindaminch.com]

Hello!

To answer the question about template tags in javascript, i.e. $.post("{% url 'upvote' %}", {answer_id:answerid}) I

This works when your js is written in the template, as you have it, but if you ever want to move that JavaScript into a separate .js file, it will break. That’s because right now your file is being run through the Django templating engine, but a stand-alone js file wouldn’t be. What I usually do is put a data attribute on a convenient element and then get it in the way that Stephen suggests below.

So I would have <i class="upvote” data-answer-id="{{answer.id}}” data-url="{% url 'upvote' %}", {answer_id:answerid"}>&#8593</I> in my html, and then in my javascript, something like this:

$(".upvote").click( function () {

            let answerid = $(this).data("answer-id");
            console.log(answerid);
            $.post($(this).data(“url’), {answer_id:answerid});
});

Good luck, hope this helps!

Melinda

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