title: Browser support for JavaScript versions
body: <p>We are starting a project and want to be cross-browser compatible - this would seem to suggest that we need to ensure that the version of JavaScript we're using is works in all of the browsers we intend to support. Is the following a reasonable way to test to see what the JavaScript level works in each browser?</p>
  
  <pre><code>&lt;script language="javascript1.0"&gt;alert("Your browser at least supports JavaScript 1.0");&lt;/script&gt;
  &lt;script language="javascript1.1"&gt;alert("Your browser at least supports JavaScript 1.1");&lt;/script&gt;
  &lt;script language="javascript1.2"&gt;alert("Your browser at least supports JavaScript 1.2");&lt;/script&gt;
  &lt;script language="javascript1.3"&gt;alert("Your browser at least supports JavaScript 1.3");&lt;/script&gt;
  &lt;script language="javascript1.4"&gt;alert("Your browser at least supports JavaScript 1.4");&lt;/script&gt;
  &lt;script language="javascript1.5"&gt;alert("Your browser at least supports JavaScript 1.5");&lt;/script&gt;
  &lt;script language="javascript1.6"&gt;alert("Your browser at least supports JavaScript 1.6");&lt;/script&gt;
  &lt;script language="javascript1.7"&gt;alert("Your browser at least supports JavaScript 1.7");&lt;/script&gt;
  &lt;script language="javascript1.8"&gt;alert("Your browser at least supports JavaScript 1.8");&lt;/script&gt;
  </code></pre>
  
  <p>Obviously the list of tests could be extended as further JavaScript versions are released.</p>
  
  <p>Is there a better way (or source) for this information?</p>
  
  <p>By the way, I did see the <a href="https://en.wikipedia.org/wiki/JavaScript#Version_history" rel="nofollow">Wikipedia page on JavaScript versions</a> and it doesn't seem to correspond to the results I get when I run the code snippet above.</p>
  
  <p>My results are:</p>
  
  <p><strong>Firefox 43.0.4</strong> - reports as supporting JavaScript 1.0 through 1.5<br>
  <strong>IE 10.0.9200.17566</strong> - reports as supporting JavaScript 1.1 through 1.3<br>
  <strong>Chrome Version 47.0.2526.111 m</strong> - reports as supporting JavaScript 1.0 through 1.7<br>
  <strong>Safari 5.1.7 (7534.57.2)</strong> - reports as supporting JavaScript 1.0 through 1.7<br>
  <strong>Opera 34.0.2036.50</strong> - reports as supporting JavaScript 1.0 through 1.7<br></p>