Why Does Firefox Not Support ES2015 Imports?

Can ES2015 Import Work in Firefox?

Despite placing your import statement at the top level of your t1.js file, you encounter the error: "SyntaxError: import declarations may only appear at top level of a module." This suggests that Firefox may not be fully supporting ES2015 import functionality.

Understanding the Correct Top-Level Requirement

While your import statement is located at the beginning of t1.js, it is crucial to note that the file itself must explicitly indicate that it's loaded as a module. Simply placing the import statement at the top of a non-module file will not suffice.

How to Enable Module Loading in Firefox

To resolve the issue, you need to add the "type" attribute to your script tag, specifying that it's a module:

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

Browser Compatibility

ES2015 import/export functionality is currently fully supported in the following browser versions and later (check caniuse.com for the most up-to-date list):

• Firefox 60
• Chrome (desktop) 65
• Chrome (Android) 66
• Safari 11

Enabling Module Support in Older Browsers

For older browser versions, you may need to enable certain flags:

• Chrome Canary 60: "Experimental Web Platform" flag
• Firefox 54: "dom.moduleScripts.enabled" setting
• Edge 15: "Experimental JavaScript Features" flag

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