Django es rápido y sucio: pasar datos en JavaScript sin AJAX

Hola, Khabrovites. Para los futuros alumnos del curso "Desarrollador web en Python" hemos preparado una traducción del material.

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Si queremos pasar datos de Django a JavaScript, solemos hablar de API, serializadores, llamadas JSON y AJAX. Esto suele complicarse por la presencia de React o Angular en el frente.

- – .

, Django :

from django.db import models


class SomeDataModel(models.Model):
    date = models.DateField(db_index=True)
    value = models.IntegerField()
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

TemplateView



:

<img alt="

from django.views.generic import TemplateView


class SomeTemplateView(TemplateView):
    template_name = 'some_template.html'
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Chart.js, AJAX, API ..

some_template.html



, ( ):

<canvas id="chart"></canvas>

<script src="https://cdn.jsdelivr.net/npm/chart.js@2.9.4/dist/Chart.min.js"></script>
<script>
window.onload = function () {
  var data = [48, -63, 81, 11, 70];
  var labels = ['January', 'February', 'March', 'April', 'May'];

  var config = {
    type: 'line',
    data: {
      labels: labels,
      datasets: [
        {
          label: 'A random dataset',
          backgroundColor: 'black',
          borderColor: 'lightblue',
          data: data,
          fill: false
        }
      ]
    },
    options: {
      responsive: true
    }
  };

  var ctx = document.getElementById('chart').getContext('2d');
  window.myLine = new Chart(ctx, config);
};
</script>
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

:

, , SomeDataModel



, :

from django.views.generic import TemplateView

from some_project.some_app.models import SomeDataModel


class SomeTemplateView(TemplateView):
    template_name = 'some_template.html'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)

        context['data'] = [
            {
                'id': obj.id,
                'value': obj.value,
                'date': obj.date.isoformat()
            }
            for obj in SomeDataModel.objects.all()
        ]

        return context
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

JavaScript Django:

<canvas id="chart"></canvas>

<script src="https://cdn.jsdelivr.net/npm/chart.js@2.9.4/dist/Chart.min.js"></script>
<script>
window.onload = function () {
  // We render via Django template
  var data = [
    {% for item in data %}
      {{ item.value }},
    {% endfor %}
  ]

  // We render via Django template
  var labels = [
    {% for item in data %}
      "{{ item.date }}",
    {% endfor %}
  ]

  console.log(data);
  console.log(labels);

  var config = {
    type: 'line',
    data: {
      labels: labels,
      datasets: [
        {
          label: 'A random dataset',
          backgroundColor: 'black',
          borderColor: 'lightblue',
          data: data,
          fill: false
        }
      ]
    },
    options: {
      responsive: true
    }
  };

  var ctx = document.getElementById('chart').getContext('2d');
  window.myLine = new Chart(ctx, config);
};

</script>
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, , , . JavaScript, JavaScript Django. JavaScript .js. JavaScript.

.

:

1. json.dumps
   
   
   
   .

   
   
   
   
   

2. <div>



id



data-json
   
   
   
   , JSON. 

   
   
   
   
   

3. <div>
   
   
   
   JavaScript, data-json



JSON.parse
   
   
   
   , .

   
   
   
   
   

, JavaScript Django, . 

AJAX.

, :

import json

from django.views.generic import TemplateView


class SomeTemplateView(TemplateView):
    template_name = 'some_template.html'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)

        context['data'] = json.dumps(
            [
                {
                    'id': obj.id,
                    'value': obj.value,
                    'date': obj.date.isoformat()
                }
                for obj in SomeDataModel.objects.all()
            ]
        )

        return context
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

JavaScript chart.js



.

some_template.html



:

{% load static %}

<div style="display: none" id="jsonData" data-json="{{ data }}"></div>

<canvas id="chart"></canvas>

<script src="https://cdn.jsdelivr.net/npm/chart.js@2.9.4/dist/Chart.min.js"></script>
<script src="{% static 'chart.js' %}"></script>
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

div



. div



, . id



HTML-.

data-json



( - ) JSON.

, , :

function loadJson(selector) {
  return JSON.parse(document.querySelector(selector).getAttribute('data-json'));
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

chart.js



:

function loadJson(selector) {
  return JSON.parse(document.querySelector(selector).getAttribute('data-json'));
}

window.onload = function () {
  var jsonData = loadJson('#jsonData');

  var data = jsonData.map((item) => item.value);
  var labels = jsonData.map((item) => item.date);

  console.log(data);
  console.log(labels);

  var config = {
    type: 'line',
    data: {
      labels: labels,
      datasets: [
        {
          label: 'A random dataset',
          backgroundColor: 'black',
          borderColor: 'lightblue',
          data: data,
          fill: false
        }
      ]
    },
    options: {
      responsive: true
    }
  };

  var ctx = document.getElementById('chart').getContext('2d');
  window.myLine = new Chart(ctx, config);
};
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, - . :

 

- , . JavaScript , . SPA ( React).

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"Web- Python".



Demo day .