Can't get WebGL to Interact with browser scripting

Hi all.

I keep getting errors when trying to interact with browser scripting.

I've followed a bunch of examples, but let's use the standard example from the Unity manual: https://docs.unity3d.com/Manual/webgl-interactingwithbrowserscripting.html

Using Unity 2018.2.18f1

In a folder called Plugins I've created a file called test.jslib:

 mergeInto(LibraryManager.library, {
  
   Hello: function () {
     window.alert("Hello, world!");
   },
  
   HelloString: function (str) {
     window.alert(Pointer_stringify(str));
   },
  
   PrintFloatArray: function (array, size) {
     for(var i = 0; i < size; i++)
     console.log(HEAPF32[(array >> 2) + i]);
   },
  
   AddNumbers: function (x, y) {
     return x + y;
   },
  
   StringReturnValueFunction: function () {
     var returnStr = "bla";
     var bufferSize = lengthBytesUTF8(returnStr) + 1;
     var buffer = _malloc(bufferSize);
     stringToUTF8(returnStr, buffer, bufferSize);
     return buffer;
   },
  
   BindWebGLTexture: function (texture) {
     GLctx.bindTexture(GLctx.TEXTURE_2D, GL.textures[texture]);
   },
  
 });
  

I got a gameobject containt a script called NewBehaviourScript:

 using UnityEngine;
 using System.Runtime.InteropServices;
  
 public class NewBehaviourScript : MonoBehaviour {
  
     [DllImport("__Internal")]
     private static extern void Hello();
  
     [DllImport("__Internal")]
     private static extern void HelloString(string str);
  
     [DllImport("__Internal")]
     private static extern void PrintFloatArray(float[] array, int size);
  
     [DllImport("__Internal")]
     private static extern int AddNumbers(int x, int y);
  
     [DllImport("__Internal")]
     private static extern string StringReturnValueFunction();
  
     [DllImport("__Internal")]
     private static extern void BindWebGLTexture(int texture);
  
     void Start() {
         Hello();
      
         HelloString("This is a string.");
      
         float[] myArray = new float[10];
         PrintFloatArray(myArray, myArray.Length);
      
         int result = AddNumbers(5, 7);
         Debug.Log(result);
      
         Debug.Log(StringReturnValueFunction());
      
         var texture = new Texture2D(0, 0, TextureFormat.ARGB32, false);
         BindWebGLTexture(texture.GetNativeTextureID());
     }
 }
 

But when building and running the WebGL player I get this error:

 An error occurred running the Unity content on this page. See your browser JavaScript console for more info. The error was:
 uncaught exception: abort(-1) at jsStackTrace (TemplateTest.wasm.framework.unityweb:2:22127)
 stackTrace (TemplateTest.wasm.framework.unityweb:2:22298)
 onAbort@file:///D:/Thom/Unity/Arti/Projects/Builds/TemplateTest/Build/UnityLoader.js:4:10645
 abort (TemplateTest.wasm.framework.unityweb:2:481204)
 _Hello (TemplateTest.wasm.framework.unityweb:2:46724)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[27384]:0x8ad47d (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[26720]:0x8a0acf)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[27676]:0x8c0345
 d38edf9076c603d4878e64a366122da4 [UnityLoader.d38edf9076c603d4878e64a366122da4/Module.dynCall_iiiii] (TemplateTest.wasm.framework.unityweb:2:1)
 invoke_iiiii (TemplateTest.wasm.framework.unityweb:2:354531)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[24271]:0x84f271 (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[24625]:0x85c523)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[1925]:0x9a32d (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[1924]:0x9a296)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[3415]:0x100cf7 (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[3410]:0x100a05)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[6314]:0x267100 (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[4101]:0x16ac7f)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[7056]:0x2b9599 (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[6409]:0x270d9f)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[6409]:0x270db6 (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[6404]:0x26ffcc)
 @blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[6398]:0x26e852 (blob:null/6a898df7-bfc2-4be5-b2d9-be16afff3d52 line 2 > WebAssembly.instantiate:wasm-function[24873]:0x866f5a)
 d38edf9076c603d4878e64a366122da4 [UnityLoader.d38edf9076c603d4878e64a366122da4/Module.dynCall_v] (TemplateTest.wasm.framework.unityweb:2:468735)
 browserIterationFunc (TemplateTest.wasm.framework.unityweb:2:131228)
 runIter (TemplateTest.wasm.framework.unityweb:2:134320)
 Browser_mainLoop_runner (TemplateTest.wasm.framework.unityweb:2:132765)

I've followed multiple other examples, as far as I could find them, but I've always seem to be getting these kind of errors.

Does it have something to do with WebAssembly? is the .jslib file incorrect? How would I get this to work?

Thanks in advance!