How to check if a browser supports Polymer?

Question

How am I able to check (JS or HTML code) whether Polymer is supported by the current browser or not?

Answer 1

Short answer:

Quick test: Firefox 38.0.5 alerts "No", while Chrome 44.0.2403.130 m alerts "Yes"

function supportsPolymer() {
  return 'content' in document.createElement('template') && 'import' in document.createElement('link') && 'registerElement' in document && document.head.createShadowRoot;
}

if(supportsPolymer()) {
  
  //Good to go
  alert("Yes");
  
} else {
  
  //Is not supported
  alert("No");
  
}

Detailed answer:

You've to check this list on Polymer's website.

• Template
• HTML Imports
• Custom Elements
• Shadow DOM

These features have to be supported:

• http://www.html5rocks.com/en/tutorials/webcomponents/template/

function supportsTemplate() {
  return 'content' in document.createElement('template');
}

if (supportsTemplate()) {
  // Good to go!
} else {
  // Use old templating techniques or libraries.
}

---

• https://www.polymer-project.org/0.5/platform/html-imports.html

function supportsImports() {
  return 'import' in document.createElement('link');
}

if (supportsImports()) {
  // Good to go!
} else {
  // Use other libraries/require systems to load files.
}

---

• https://www.polymer-project.org/0.5/platform/custom-elements.html

function supportsCustomElements() {
  return 'registerElement' in document;
}

if (supportsCustomElements()) {
  // Good to go!
} else {
  // Use other libraries to create components.
}

---

• https://www.polymer-project.org/0.5/platform/shadow-dom.html

How to check if a browser supports shadow DOM

if(document.head.createShadowRoot) {
    // I can shadow DOM
} else {
    // I can't
}

In a function:

 function supportsShadowDom() {
   return document.head.createShadowRoot;
 }

Untested version in the style of the previous snippets:

 function supportsShadowDom() {
   return 'createShadowRoot' in document;
 }

---

Okay, after you've implemented every function you can do something like this:

 if (supportsCustomElements() && supportsTemplate() && supportsImports() && supportsShadowDom()) {
   // Good to go!
 } else {
   // Use other libraries to create components.
 }

This is the current matrix from https://github.com/WebComponents/webcomponentsjs#browser-support:

<table><thead>
<tr>
<th>Polyfill</th>
<th align="center">IE10</th>
<th align="center">IE11+</th>
<th align="center">Chrome*</th>
<th align="center">Firefox*</th>
<th align="center">Safari 7+*</th>
<th align="center">Chrome Android*</th>
<th align="center">Mobile Safari*</th>
</tr>
</thead><tbody>
<tr>
<td>Custom Elements</td>
<td align="center">~</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
</tr>
<tr>
<td>HTML Imports</td>
<td align="center">~</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
</tr>
<tr>
<td>Shadow DOM</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
</tr>
<tr>
<td>Templates</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
<td align="center">✓</td>
</tr>
</tbody></table>

This may be interesting, too: https://github.com/webcomponents/webcomponentsjs/issues/26