Nested Javascript Templates … is this possible / valid?

Is it possible to have nested JavaScript template tags e.g.

<script id="Product" type="text/html">
    <div class="product">
        ....
        <div class="features">
            <script id="Features" type="text/html">
                <div class="feature">
                    ...
                </div>
            </script>
        </div>
        ...
    </div>
</script>

When the template "Product" is evaluated the feature template is now available as a template that I can call when I'm ready.

When I try this method in my browser, I notice some elements appear in the wrong order as if I forgot an end tag somewhere.

However when I remove the nested template (Feature) it is all good ...

Wondering if there was proper way of achieving this.

Answers:

Answer

You can't nest script tags. The way script tags work, the browser reads the opening tag and then starts building up a string of the code therein without interpreting that code at all. It stops doing that the first time it sees the exact sequence < / s c r i p t >. The browser will always stop at the first of those it finds, and crucially it ignores any intervening opening tag sequence, like < s c r i p t >. This is because the browser doesn't parse the script code, that's not its job. It's a separation of concerns thing. (script tags probably shouldn't be tags at all, but rather something more like a CDATA structure. But they're what we have.)

E.g., from the browser's point of view:

<script id="Product" type="text/html">              SCRIPT STARTS HERE
    <div class="product">                           SCRIPT CODE CONTINUES
        ....                                        SCRIPT CODE CONTINUES
        <div class="features">                      SCRIPT CODE CONTINUES
            <script id="Features" type="text/html"> SCRIPT CODE CONTINUES (*NOT* START OF SCRIPT)
                <div class="feature">               SCRIPT CODE CONTINUES
                    ...                             SCRIPT CODE CONTINUES
                </div>                              SCRIPT CODE CONTINUES
            </script>                               SCRIPT ENDS
        </div>                                      ENDING `div` TAG (probably mis-matched)
        ...
    </div>
</script>                                           MIS-MATCHED ENDING `script` TAG

Now, if you're using a server-side templating engine of some kind that will replace those script tags with markup and then send the updated markup to the browser, then it's up to the templating engine whether it supports nesting. Browsers do not.

Answer

You can use <style type="text/html"></style> or <noscript></noscript> to wrap your <script></script> tag.

I think <noscript> is better than <style>

example:

<noscript id="s">
  <div class="r">
    <p>{%= o.rand %}</p>
    <script>
      console.log('sdf');
    </script>
  </div>
</noscript>

<style id="s" type="text/html">
  <div class="r">
    <p>{%= o.rand %}</p>
    <script>
      console.log('sdf');
    </script>
  </div>
</style>

Answer

Are okay with using jQuery? If so, this very possible (and even, dare I say, common):

http://blog.reybango.com/2010/07/12/jquery-javascript-templates-tutorial-nesting-templates/

Answer

Sometimes I think I want nested scipt tags for templating, but this is what you have to do instead:

Script 1

 <script id="Product" type="text/html">
     <div class="product">
         ....
         <div class="features">
             <!-- INSERT FEATURES HERE -->   
         </div>
         ...
     </div>
 </script>

Script 2

 <script id="Product_Features" type="text/html">
     <div class="feature">

     </div>
 </script>

You can 'namespace' the ID if you really want, to indicate it is a 'child' template. This makes it clearer is it not intended to be used by itself (obviously this is up to you if it makes sense or not).

After reading T.J.s answer this became the only obvious alternative to what I originally thought I wanted (nested scripts).

However, you probably don't need nested templates unless you need to make a choice as to which 'child' template is used. If there's only one possible layout for the child template then just use a 'foreach' according to your template engine.

Answer

Yes, it is possible to have nested <script> tags (with XHTML application/xhtml+xml):

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>XHTML nested &lt;script&gt;</title>
</head>
<body>
  <script id="Product" type="text/html">
    <div class="product">
      ....
      <div class="features">
        <script id="Features" type="text/html">nested
          <div class="feature">
            ...
          </div>
        </script>
      </div>
      ...
    </div>
  </script>
</body>
</html>

Code snippet does not support XHTML, I have to use iframe with data URL:

<iframe src="data:application/xhtml+xml,%3Chtml%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1999%2Fxhtml%22%20contenteditable%3D%22true%22%3E%3Chead%3E%3Ctitle%3EXHTML%20nested%20%26lt%3Bscript%26gt%3B%3C%2Ftitle%3E%3C%2Fhead%3E%3Cbody%3E%3Cstyle%3Estyle%2C%20script%20%7B%20display%3A%20block%3B%20font-family%3A%20monospace%3B%20white-space%3A%20pre%3B%20padding-left%3A%2010px%20%7D%0Astyle%20%7B%20border-left%3A%2010px%20solid%20%2398A6C0%20%7D%0Ascript%20%7B%20border-left%3A%2010px%20solid%20%23D6F034%20%7D%3C%2Fstyle%3E%3Cscript%20id%3D%22Product%22%20type%3D%22text%2Fhtml%22%3Eouter%0A%20%20%20%20%3Cdiv%20class%3D%22product%22%3E%0A%20%20%20%20%20%20%20%20....%0A%20%20%20%20%20%20%20%20%3Cdiv%20class%3D%22features%22%3E%0A%20%20%20%20%20%20%20%20%20%20%20%20%3Cscript%20id%3D%22Features%22%20type%3D%22text%2Fhtml%22%3Einner%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%3Cdiv%20class%3D%22feature%22%3E%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20...%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%3C%2Fdiv%3E%0A%20%20%20%20%20%20%20%20%20%20%20%20%3C%2Fscript%3E%0A%20%20%20%20%20%20%20%20%3C%2Fdiv%3E%0A%20%20%20%20%20%20%20%20...%0A%20%20%20%20%3C%2Fdiv%3E%0A%3C%2Fscript%3E%3C%2Fbody%3E%3C%2Fhtml%3E" width="100%"></iframe>

Yes, it is possible to have nested <script> tags in HTML DOM:

productScript = document.createElement('script')
productScript.setAttribute('id', 'Product')
productScript.setAttribute('type', 'text/html')
productScript.appendChild(document.createTextNode('outer'))

product = document.createElement('div')
product.setAttribute('class', 'product')
product.appendChild(document.createTextNode(`
        ....
        `))

features = document.createElement('div')
features.setAttribute('class', 'features')

featuresScript = document.createElement('script')
featuresScript.setAttribute('id', 'Features')
featuresScript.setAttribute('type', 'text/html')
featuresScript.appendChild(document.createTextNode('inner'))

feature = document.createElement('div')
feature.setAttribute('class', 'feature')
feature.appendChild(document.createTextNode(`
        ...
    `))

featuresScript.appendChild(feature)
features.appendChild(featuresScript)
product.appendChild(document.createTextNode(`
        ...
    `))
product.appendChild(features)
productScript.appendChild(product)
document.body.appendChild(productScript)
script[type="text/html"] {
  display: block;
  font-family: monospace;
  white-space: pre;
  padding-left: 10px;
  border-left: 10px solid #D6F034
}

No, it is not possible to have nested <script> tags in HTML serialization. Its content is not parsed:

let product = document.getElementById('Product')
console.log(product.textContent)
<script id="Product" type="text/html">
    <div class="product">
        ....
        <div class="features">
            <script id="Features" type="text/html">nested
                <div class="feature">
                    ...
                </div>
            </script>
        </div>
        ...
    </div>
</script>

Answer

Try this:

<script id="Product" type="text/html">
<!--
    <div class="product">
        ....
        <div class="features">
            <script id="Features" type="text/html">
                <div class="feature">
                    ...
                </div>
            </script>
        </div>
        ...
    </div>
-->
</script>

When you need to get it:

document.getElementById("Product").text.replace(/(?:^\s*<!--\s*)|(?:\s*-->\s*$)/g, "");

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