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

Question

I'm using ArcGIS JSAPI 4.12 and wish to use Spatial Illusions to draw military symbols on a map.

When I add milsymbol.js to the script, the console returns error

Uncaught SyntaxError: Cannot use import statement outside a module`

so I add type="module" to the script, and then it returns

Uncaught ReferenceError: ms is not defined

Here's my code:

<link rel="stylesheet" href="https://js.arcgis.com/4.12/esri/css/main.css">
<script src="https://js.arcgis.com/4.12/"></script>
<script type="module" src="milsymbol-2.0.0/src/milsymbol.js"></script>

<script>
    require([
        "esri/Map",
        "esri/views/MapView",
        "esri/layers/MapImageLayer",
        "esri/layers/FeatureLayer"
    ], function (Map, MapView, MapImageLayer, FeatureLayer) {

        var symbol = new ms.Symbol("SFG-UCI----D", { size: 30 }).asCanvas(3);
        var map = new Map({
            basemap: "topo-vector"
        });

        var view = new MapView({
            container: "viewDiv",
            map: map,
            center: [121, 23],
            zoom: 7
        });
    });
</script>

So, whether I add type="module" or not, there are always errors. However, in the official document of Spatial Illusions, there isn't any type="module" in the script. I'm now really confused. How do they manage to get it work without adding the type?

File milsymbol.js

import { ms } from "./ms.js";

import Symbol from "./ms/symbol.js";
ms.Symbol = Symbol;

export { ms };

Answer 1

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>

Answer 2

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.

Answer 3

Update For Node / NPM

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

{
  // ...
  "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.

Answer 4

I was also facing the same issue until I added the type="module" to the script.

Before it was like this

<script src="../src/main.js"></script>

And after changing it to

<script type="module" src="../src/main.js"></script>

It worked perfectly.

Answer 5

I solved this issue by doing the following:

When using ECMAScript 6 modules from the browser, use the .js extension in your files and in the script tag add type = "module".

When using ECMAScript 6 modules from a Node.js environment, use the extension .mjs in your files and use this command to run the file:

node --experimental-modules filename.mjs

Edit: This was written when node12 was the latest LTS, this does not apply on node 14 LTS.

Answer 6

I resolved my case by replacing "import" by "require".

// import { parse } from 'node-html-parser';
parse = require('node-html-parser');

Answer 7

I don't know whether this has appeared obvious here. I would like to point out that as far as client-side (browser) JavaScript is concerned, you can add type="module" to both external as well as internal js scripts.

Say, you have a file 'module.js':

var a = 10;
export {a};

You can use it in an external script, in which you do the import, eg.:

<!DOCTYPE html><html><body>
<script type="module" src="test.js"></script><!-- Here use type="module" rather than type="text/javascript" -->
</body></html>

test.js:

import {a} from "./module.js";
alert(a);

You can also use it in an internal script, eg.:

<!DOCTYPE html><html><body>
<script type="module">
    import {a} from "./module.js";
    alert(a);
</script>
</body></html>

It is worthwhile mentioning that for relative paths, you must not omit the "./" characters, ie.:

import {a} from "module.js";     // this won't work

Answer 8

For me, it was caused before I referred a library (specifically typeORM, using the ormconfig.js file, under the entities key) to the src folder, instead of the dist folder...

   "entities": [
      "src/db/entity/**/*.ts", // Pay attention to "src" and "ts" (this is wrong)
   ],

instead of

   "entities": [
      "dist/db/entity/**/*.js", // Pay attention to "dist" and "js" (this is the correct way)
   ],

Answer 9

I'm coding on vanilla js. If you're doing same, simply add a type="module" to your script tag.

That is, previous code:
<script src="./index.js"></script>

Updated Code:
<script type="module" src="./index.js"></script>

Answer 10

This error in REACT. following steps

1. Go to Project Root Directory Package.json file

2. add "type":"module";

3. Save it and Restart Server

Answer 11

Adding the why this occurs and more possible cause. A lot of interfaces still do not understand ES6 Javascript syntax/features, hence there is need for Es6 to be compiled to ES5 whenever it is used in any file or project. The possible reasons for the SyntaxError: Cannot use import statement outside a module error is you are trying to run the file independently, you are yet to install and set up an Es6 compiler such as Babel or the path of the file in your runscript is wrong/not the compiled file. If you will want to continue without a compiler the best possible solution is to use ES5 syntax which in your case would be var ms = require(./ms.js); this can later be updated as appropriate or better still setup your compiler and ensure your file/project is compiled before running and also ensure your run script is running the compiled file usually named dist, build or whatever you named it and the path to the compiled file in your runscript is correct.

Answer 12

The error is triggered because the file you're linking to in your HTML file is the unbundled version of the file. To get the full bundled version you'll have to install it with npm:

npm install --save milsymbol

This downloads the full package to your node_modules folder.

You can then access the standalone minified JavaScript file at node_modules/milsymbol/dist/milsymbol.js

You can do this in any directory, and then just copy the below file to your /src directory.

Answer 13

for me helped:

1. in ts file used: import prompts from "prompts";
2. and use "module": "commonjs" in tsconfig.json

Answer 14

TypeScript, React, index.html

    //conf.js:
    window.bar = "bar";
    
   //index.html 
    <script type="module" src="./conf.js"></script>
    
    //tsconfig.json
    "include": ["typings-custom/**/*.ts"]
    
    //typings-custom/typings.d.ts
    declare var bar:string;

    //App.tsx
    console.log('bar', window.bar);
    or
    console.log('bar', bar);

Answer 15

What I did in my case was to update

"lib": [
      "es2020",
      "dom"
    ]

with

"lib": [
  "es2016",
  "dom"
]

in my tsconfig.json file

Answer 16

I ran into this error while trying to use import express

Instead of   import express from 'express';

I used   const express = require('express');

Hope it works!

Answer 17

It's because you haven't exported, the ts file requires a export class format, whereas in js file we would use exports function.

So, we have to use var_name = require("<pathfile>") to use that file functions.

Answer 18

Just add .pack between the name and the extension in the <script> tag in src. i.e.:

<script src="name.pack.js">
// code here
</script>