Importing Modules in Firefox: Unraveling the SyntaxError

ES2015 Import Woes in Firefox

Firefox users have encountered a puzzling error while attempting to leverage ES2015 import and export features:

Error:

SyntaxError: import declarations may only appear at top level of a module

This error occurs despite placing the import statement at the top level of the script. This raises the question: is import/export support in Firefox deficient?

The Solution:
Contrary to intuition, the error stems from a missing module declaration. To enable modular loading, explicitly indicate that the script is a module by adding the type="module" attribute:

<code class="html"><script src="t1.js" type="module"></script></code>

This declaration allows the use of import statements within the module.

Browser Support:
Import/export is fully supported in modern browsers:

• Firefox 60
• Chrome 65 (desktop and Android)
• Safari 1.1

For earlier browser versions, enabling experimental flags may be required:

• Chrome Canary 60: Enable the "Experimental Web Platform" flag.
• Firefox 54: Set the "dom.moduleScripts.enabled" preference in about:config.
• Edge 15: Enable the "Experimental JavaScript Features" flag.

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