fetch('/api/products/' + productId)

.then(function (response) { return response.json(); })

.then(function (apiResponse) {

if (apiResponse.isError) {

// get the robots meta tag

var metaRobots = document.querySelector('meta[name="robots"]');

// if there was no robots meta tag, add one

if (!metaRobots) {

metaRobots = document.createElement('meta');

metaRobots.setAttribute('name', 'robots');

document.head.appendChild(metaRobots);

}

// tell Googlebot to exclude this page from the index

metaRobots.setAttribute('content', 'noindex');

// display an error message to the user

errorMsg.textContent = 'This product is no longer available';

return;

}

// display product information

// ...

});

<!-- Hotjar Tracking Code for https://sites.google.com/view/jsdglefutur -->

<script>

(function(h,o,t,j,a,r){

h.hj=h.hj||function(){(h.hj.q=h.hj.q||[]).push(arguments)};

h._hjSettings={hjid:2828450,hjsv:6};

a=o.getElementsByTagName('head')[0];

r=o.createElement('script');r.async=1;

r.src=t+h._hjSettings.hjid+j+h._hjSettings.hjsv;

a.appendChild(r);

})(window,document,'https://static.hotjar.com/c/hotjar-','.js?sv=');

</script>

<nav>

<ul>

<li><a href="#/products">Our products</a></li>

<li><a href="#/services">Our services</a></li>

</ul>

</nav>

<h1>Welcome to example.com!</h1>

<div id="placeholder">

<p>Learn more about <a href="#/products">our products</a> and <a href="#/services">our services</p>

</div>

<script>

window.addEventListener('hashchange', function goToPage() {

// this function loads different content based on the current URL fragment

const pageToLoad = window.location.hash.slice(1); // URL fragment

document.getElementById('placeholder').innerHTML = load(pageToLoad);

});

</script>

<script>

class MyComponent extends HTMLElement {

constructor() {

super();

this.attachShadow({ mode: 'open' });

}

connectedCallback() {

let p = document.createElement('p');

p.innerHTML = 'Hello World, this is shadow DOM content. Here comes the light DOM: <slot></slot>';

this.shadowRoot.appendChild(p);

}

}

window.customElements.define('my-component', MyComponent);

</script>

<my-component>

<p>This is light DOM content. It's projected into the shadow DOM.</p>

<p>WRS renders this content as well as the shadow DOM content.</p>

</my-component>

<!-- Hotjar Tracking Code for https://sites.google.com/view/jsdglefutur -->

<script>

(function(h,o,t,j,a,r){

h.hj=h.hj||function(){(h.hj.q=h.hj.q||[]).push(arguments)};

h._hjSettings={hjid:2828450,hjsv:6};

a=o.getElementsByTagName('head')[0];

r=o.createElement('script');r.async=1;

r.src=t+h._hjSettings.hjid+j+h._hjSettings.hjsv;

a.appendChild(r);

})(window,document,'https://static.hotjar.com/c/hotjar-','.js?sv=');

</script>