WebGL Javascript plugin not working, missing function

I'm exploring some functionalities within WebGL to see how to get things done that way. But I'm having trouble getting a javascript plugin working within a build.

I used this documentation to get started:
https://docs.unity3d.com/560/Documentation/Manual/webgl-interactingwithbrowserscripting.html

The build I made running at:
https://jdmulti.nl/research/jdmulti_modelviewer/

Build with: Unity 2018.2.0f2
Running in: Chrome 67.0.3396.99
Operation System: Windows 7

I've created an javascript plugin in: Assets/Plugins/WebGL/ImageUploader.jslib with this code:

Code (JavaScript):

1. Assets/Plugins/WebGL/ImageUploader.jslib
2. mergeInto(LibraryManager.library,
3. {
4.   Hello: function ()
5.   {
6.     window.alert("Hello, world!");
7.   },
8. });

Then I created an C# script doing this:

Code (CSharp):

1. using UnityEngine;
2. using System.Runtime.InteropServices;
3.  
4. public class ImageUploader : MonoBehaviour
5. {
6.     [DllImport("__Internal")]
7.     private static extern void Hello();
8.  
9.     public void OnButtonUpload()
10.     {
11.         Hello();
12.     }
13. }

In the view I've got a button which will execute the function: 'OnButtonUpload' when pressed. But when I test it locally or on my server I won't get it successfully run and instead get the error:

Code (CSharp):

1. UnityLoader.js:4 missing function: Hello
2. printErr @ UnityLoader.js:4
3.  
4. Invoking error handler due to
5. Uncaught abort(-1) at Error
6.     at jsStackTrace (WebGL.wasm.framework.unityweb:2:22127)
7.     at stackTrace [Object.stackTrace] (WebGL.wasm.framework.unityweb:2:22298)
8.     at Object.onAbort (https://jdmulti.nl/research/jdmulti_modelviewer/Build/UnityLoader.js:4:10650)
9.     at abort (WebGL.wasm.framework.unityweb:2:481498)
10.     at _Hello (WebGL.wasm.framework.unityweb:2:46544)
11.     at wasm-function[23228]:1
12.     at wasm-function[14281]:273
13.     at wasm-function[14474]:22
14.     at wasm-function[14500]:104
15.     at wasm-function[12688]:77
16.     at wasm-function[12689]:15
17.     at wasm-function[12458]:152
18.     at wasm-function[12462]:100
19.     at wasm-function[22190]:114
20.     at wasm-function[29565]:20
21.     at dynCall_viiii [Object.UnityLoader.522d0a97dcf11b9129d21cebf76de72a.Module.dynCall_viiii] (WebGL.wasm.framework.unityweb:2:473723)
22.     at invoke_viiii (WebGL.wasm.framework.unityweb:2:373474)
23.     at wasm-function[27267]:341
24.     at wasm-function[12386]:11
25.     at wasm-function[12633]:1231
26.     at wasm-function[12632]:251
27.     at wasm-function[12631]:7
28.     at wasm-function[12626]:106
29.     at wasm-function[12390]:46
30.     at wasm-function[12429]:523
31.     at wasm-function[27958]:16
32.     at wasm-function[29539]:20
33.     at dynCall_iiiii [Object.UnityLoader.522d0a97dcf11b9129d21cebf76de72a.Module.dynCall_iiiii] (WebGL.wasm.framework.unityweb:2:462887)
34.     at invoke_iiiii (WebGL.wasm.framework.unityweb:2:356649)
35.     at wasm-function[24148]:170
36.     at wasm-function[24286]:36
37.     at wasm-function[2102]:67
38.     at wasm-function[2101]:109
39.     at wasm-function[6510]:473
40.     at wasm-function[6498]:5
41.     at wasm-function[8865]:721
42.     at wasm-function[8864]:3
43.     at wasm-function[7252]:30
44.     at wasm-function[6600]:147
45.     at wasm-function[6600]:170
46.     at wasm-function[6595]:525
47.     at wasm-function[6589]:200
48.     at wasm-function[24759]:12
49.     at dynCall_v [Object.UnityLoader.522d0a97dcf11b9129d21cebf76de72a.Module.dynCall_v] (WebGL.wasm.framework.unityweb:2:468842)
50.     at browserIterationFunc (WebGL.wasm.framework.unityweb:2:133798)
51.     at runIter [Object.runIter] (WebGL.wasm.framework.unityweb:2:136871)
52.     at Browser_mainLoop_runner (WebGL.wasm.framework.unityweb:2:135333)
53.  

I've been trying several things which included removing the path within the javascript plugin and the path within Unity is also correct. Is there a place where I need to drag the plugin file into to have it included in my build? I'm clueless at the moment.

Another question, is there a way to debug javascript plugins within the editor as build times take some time before you can test it, someone has a good workflow for that?

 

the sample is work for me
1.
try to replace the line1 at ImageUploader.jslib

Code (JavaScript):

1. Assets/Plugins/WebGL/ImageUploader.jslib

to

Code (CSharp):

1. //Assets/Plugins/WebGL/ImageUploader.jslib

2.
select "ImageUploader.jslib" in UnityEditor and check the Inspector.
and check "Select platforms for plugin" -> "WebGL" is already on?