WebGL: JavaScript call function from C#, how to get C# function’s return value?

Unity Engine
1 
public class World : MonoBehaviour
{
    public string PLog(string str)
    {
        Debug.Log("Log: " + str);
        return'success!';
    }
}

var str = unityInstance.SendMessage("World", "PLog", "hello");
console.log(str);  // success!
2

I think I find the solution:
jslib:

mergeInto(LibraryManager.library, {
    On: function(type, cb) {
        window.addEventListener(Pointer_stringify(type), cb);
    },

    Emit: function(type, data) {
        window.dispatchEvent(new Event(Pointer_stringify(type)), Pointer_stringify(data));
    },
});

unity c#:

    public void PLog(string str)
    {
        Emit("send", str);
    }

browser js:

window.addEventListener('send', (str)=>{
  console.log('log', str);
});

unityInstance.SendMessage("World", "PLog", "Hello")
3

Don’t use Pointer_stringify, it is no longer supported in 2021.2 and onwards.

For examples look at the documentation

2 Likes
5

Nice! My code:

jslib

mergeInto(LibraryManager.library, {
    Emit: function(type, data) {
        var eventWithData = new CustomEvent(Pointer_stringify(type), { detail: Pointer_stringify(data) });
        window.dispatchEvent(eventWithData);
    },
});

c#

public void loadset(string parameters)
{
    string[ ] parameterArray = parameters.Split(',');
    string parentName = parameterArray[0];
    string fileName= parameterArray[1];
    Emit("send", parentName+","+fileName);
}

html js

var FilesString;
window.addEventListener('send', function(str) {
    console.log('log', str);
    FilesString=str;
});

function set_js( parentName,fileName) {
    var parameters = parentName.toString() + ',' + fileName.toString();
    gameInstance.SendMessage("goname", "loadset",parameters);
    return FilesString.detail;
};
6

In your hosted JavaScript code

<!DOCTYPE html>
<html lang="en-us">
    <head>
      <meta charset="utf-8">
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
      <title>Unity WebGL Player</title>
    </head>
    <body>

    <script>
        var myCustomFunction= function(msg) {
          console.log("Calling from Unity: " + msg)
        }
    </script>

  </body>
</html>

In unity
Create a file anyname.jslib under Assets/Plugins/

Add your myCustomFunction

mergeInto(LibraryManager.library, {
    CallExternalJs: function (message) {
        myCustomFunction(UTF8ToString(message));
    },
});

Finally in your c# script call this myCustomFunction

Like this:

public class UnityToJavaScript : MonoBehaviour
{
    // Declare the external JavaScript function
    [DllImport("__Internal")]
    private static extern void CallExternalJs(string message);

    void Start()
    {
        // Call the JavaScript function
        CallExternalJs("Hello from Unity!");
    }
    
}

That’s it. Enjoy :+1: