Jinja templating not working in script.js - flask

Question

I need to include jinja templating in element.innerHTML but jinja is not working.
Code script.js:
contentDiv.innerHTML = getContent(fragmentId);
function getContent(fragmentId) {
var pages = {
quad1: `
<form class="form-inline" method="POST" id="form1">
<h3>
<input type="number" id="quad_a1" name="input_a" class="form-control mx-2 col-1" placeholder="a">
<b>x² +</b>
<input type="number" id="quad_b1" name="input_b" class="form-control mx-2 col-1" placeholder="b">
<b>x +</b>
<input type="number" name="input_c" class="form-control mx-2 col-1" placeholder="c">
<b>=</b>
<input type="number" name="input_d" class="form-control mx-2 col-2" placeholder="Default(0)">
<button type="submit" class="btn btn-primary float-right mr-5" onclick="return empty_quad()">Solve</button>
</h3>
</form>
{{ sol }}
`,
.
.
.
};
return pages[fragmentId];
}
But the output is literally {{ sol }}, not the value of sol:
So how to access the variable sol passed through flask's render_template() in script.js?

Answer 1

You can't use jinja2 template in your js file.
First method: You have to use inline javascript in html file using <script></script> tag, and then you can access the sol variable by assigning it to javascript variable
<script> sol = "{{sol}}" </script> // {{sol}} should be between quotation marks
Second method: If you have seperate js file. you can make a div tag, define it's class and set it's id to {{sol}}. get the element by class name and then get it's id.
Html
<div class="myclass" id="{{sol}}" style="display:none"></div>
javascript
elem= document.getElementsByClassName("myclass") ;
console.log(elem.id) // this is the sol value.

Answer 2

json_script
Safely outputs a Python object as JSON, wrapped in a <script> tag, ready for use with JavaScript.
Argument: HTML “id” of the <script> tag.
For example:
{{ value|json_script:"hello-data" }}
If value is the dictionary {'hello': 'world'}, the output will be:
<script id="hello-data" type="application/json">{"hello": "world"}</script>
The resulting data can be accessed in JavaScript like this:
const value = JSON.parse(document.getElementById('hello-data').textContent);
XSS attacks are mitigated by escaping the characters “<”, “>” and “&”. For example if value is {'hello': 'world</script>&'}, the output is:
<script id="hello-data" type="application/json">{"hello": "world\\u003C/script\\u003E\\u0026amp;"}</script>
This is compatible with a strict Content Security Policy that prohibits in-page script execution. It also maintains a clean separation between passive data and executable code.
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