How to Pass Data from Flask to JavaScript in Templates for Google Maps API?

Passing Data from Flask to JavaScript in Templates

Overview

Your Flask application requires passing information from a Python dictionary to JavaScript in a template, particularly for the Google Maps API.

Solution

Render_template in Flask provides a mechanism to pass variables to templates for HTML rendering. To extend this functionality to JavaScript, you can leverage the Jinja templating engine. Here's how:

1. Incorporate Variables Anywhere: Jinja variables can be used throughout your template, including the JavaScript portion.
2. Direct Assignment: Assign JavaScript variables directly using {{ variable }}. For example, you can assign the longitude to a JavaScript variable:

<code class="javascript"><script>
  var longitude = '{{ geocode[1] }}';
</script></code>

3. Generate Array Definitions: If you want to pass an array to JavaScript, generate it as an array definition in your template:

<code class="html">  <script>
    var geocode = ['{{ geocode[0] }}', '{{ geocode[1] }}'];
  </script></code>

4. Utilize Jinja Constructs: Jinja offers more advanced constructs. For example, you can shorten the array definition using the join filter:

<code class="html"><script>
  var geocode = [{{ ', '.join(geocode) }}];
</script></code>

5. Consider tojson Filter: For more complex data structures, use the tojson filter to convert dictionaries and lists to JSON strings for JavaScript consumption:

<code class="html">  <script>
    var geocode = {{ geocode | tojson }};
  </script></code>

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