How to pass JavaScript variable to function in Jinja tag

javascript, jinja2, python

Solution

You cannot pass values from javascript to the template that way because the template is going to be rendered before the response goes back to the browser for the javascript engine to evaluate. The only way the template renderer would be able to resolve the value of `name` specified in the javascript code would be to interpret the string embedded in `<script></script>`.

Update. Let's look at your second attempt, the one that you say has worked. You have:

<body>
    <button onclick="js_fn('{{ py_fn('some_string') }}')">Click me</button>
    <script>
        function js_fn(variable) {
            alert(variable);
        }
    </script>
</body>

Presumably this is in some partial (say _index.html). A view that has `py_fn` in scope, loads _index.html, evaluates the string "py_fn('some_string')", and replaces `{{ py_fn('some_string') }}` with the result of that evaluation. Let's say `py_fn` is the identity function on strings: it's a unary function that takes a string and immediately returns it. Then, the result of evaluating "py_fn('some_string')" will be the string `'some_string'`, which will be substituted back, obtaining the final, so-called "rendered" template:

<body>
    <button onclick="js_fn('some_string')">Click me</button>
    <script>
        function js_fn(variable) {
            alert(variable);
        }
    </script>
</body>

This string will be part of the response body of the request, so the browser will dump the button on the window, evaluate the js code inside the script block, which will create a global variable `js_fn` on the `window`, which will take something and alert it. The button, when clicked on, will call `js_fn` with the constant `some_string`, always. As you can see, there is no passing of values from JS to Python/Flask.

Problem

``` <script> function myFunction() { var name = "some_string"; var display = "{{ python_function(name) }}"; alert(display); } </script> ``` Above Javascript is writen in jinja2 template. It is supposed to pass javascript variable (i.e. var name) value to python function in macro. I know above code won't solve my purpose as I am not passing javascript variable value correctly to macro. Does anybody have method on passing javascript variable to macro in jinja2 template?

Original source