Question

Which version of JavaScript does Google Chrome support in relation to Mozilla Firefox? In other words, does Chrome support JavaScript 1.6, 1.7, or 1.8 which Firefox also supports or some combination of them?

Answer 1

While Chrome will execute Javascript marked as “javascript1.7”, it does not support JS1.7 features like the “let” scoped variable operator.

This code will run on Firefox 3.5 but not on Chrome using V8:

<script language="javascript" type="application/javascript;version=1.7">
    function foo(){ let a = 4; alert(a); }; foo();
</script>

If you change language to “javascript1.7” and omit the type, it won’t run with JS 1.7 features in Firefox 3.5. The type section is necessary.

This seems to be related to a general WebKit bug, https://bugs.webkit.org/show_bug.cgi?id=23097; it may be that Chrome emulates the Safari behavior even though it uses a different engine.

When asked about supporting JS 1.8 features, the V8 team said they were trying to track the version used in Safari so pages would act the same in both browsers.