“Uncaught SyntaxError: Cannot use import statement outside a module” when importing ECMAScript 6

“Uncaught SyntaxError: Cannot use import statement outside a module” when importing ECMAScript 6 :

I got this error because I forgot the type="module" inside the script tag:

<script type="module" src="milsymbol-2.0.0/src/milsymbol.js"></script>

Update For Node.js / NPM

Add "type": "module" to your package.json file.

{
  // ...
  "type": "module",
  // ...
}

Note: When using modules, if you get ReferenceError: require is not defined, you’ll need to use the import syntax instead of require. You can’t natively mix and match between them, so you’ll need to pick one or use a bundler if you need to use both.


It looks like the cause of the errors are:

  1. You’re currently loading the source file in the src directory instead of the built file in the dist directory (you can see what the intended distributed file is here). This means that you’re using the native source code in an unaltered/unbundled state, leading to the following error: Uncaught SyntaxError: Cannot use import statement outside a module. This should be fixed by using the bundled version since the package is using rollup to create a bundle.
  2. The reason you’re getting the Uncaught ReferenceError: ms is not defined error is because modules are scoped, and since you’re loading the library using native modules, ms is not in the global scope and is therefore not accessible in the following script tag.

It looks like you should be able to load the dist version of this file to have ms defined on the window. Check out this example from the library author to see an example of how this can be done.

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