JavaScript Interop

Usually, to interact with JavaScript, we need to either execute some code from C# on the JavaScript side or get value(s) from the JavaScript side in C#.

How to execute JavaScript code from C#?

First of all, any JavaScript code performed inside window scope, which mean we need to know window.
After it we can write code as follow:

// our window pointer
var windowPointer = ...;
// script that will be performed in window scope
var script = '2 + 3';

SciterValue result;

// evaluate
Host.ExecuteWindowEval(windowPointer, script, out result);

var calculatedValue = Host.GetValueInt32(ref result);

Console.WriteLine("Result is " + calculatedValue);

How to execute C# code from JavaScript?

With EventHandler we can handle a lot of changes to an element, but what if we want to literally call C# methods from JavaScript? We can do this, but it will look like we are handling an event from the element.

First of all we need to markup as follow:

...
<!-- we define some element in HTML and attach our behaviour -->
<div id="myid" style="behavior: mybehaviour"></div>
...
<script>
const element = document.getElementById('myid');
const result = element.xcall("csharpmethod", "string1", 1);
console.log(result);
</script>

Second we need to handle call in C# and to do something:

public class MyHandler : ElementEventHandler {

    public MyHandler ( nint element, SciterAPIHost host ) : base ( element, host ) {}

    public override (SciterValue? value, bool handled) ScriptMethodCall ( string name, IEnumerable<SciterValue> arguments ) {
        // only if called csharpmethod
        if ( name == "csharpmethod" ) {
             // read first string parameter
             var stringParameter = arguments.ElementAt ( 0 );
             var stringValue = Host.GetValueString(ref stringParameter);
             // read second number parameter
             var intParameter = arguments.ElementAt ( 1 );
             var intValue = Host.GetValueInt32(ref intParameter);
             // create result value
             return (Host.CreateValue(stringValue + intValue), true);
        }

        return (null, false);
    }