Is it possible to support index setter through parentheses instead of brackets in V8Engine?

[ZelgiusLiu]

Hi,
I am now trying to upgrade some old projects using JScriptCodeProvider to newer version of .Net.
And when converting the JScrriptCodeProvider to ClearScript, I found some interesting differences.
As shown in the following code, I found that for JScript, it supports both getting and setting operations with index operator through parentheses; then, for V8Engine, it supports only getting value through parentheses, and setting operation can only be done when using brackets:

  var values = new PropertyBag()
  {
      ["greeting"] = "Hello",
      ["greeting2"] = "Hi"
  };

  using var js = new JScriptEngine();
  js.AddHostType(typeof(Console));
  js.AddHostObject("V", values);

  js.Execute("Console.WriteLine(V('greeting'))"); // Output: Hello
  js.Execute("V('greeting') = V('greeting2')"); // Works fine
  
  using var v8=new V8ScriptEngine();
  v8.AddHostType(typeof(Console));
  v8.AddHostObject("V", values);

  v8.Execute("Console.WriteLine(V('greeting'))"); // Output: Hi
  v8.Execute("V['greeting'] = 'Hello'"); // Works fine
  v8.Execute("V('greeting') = 'Hello'"); //ReferenceError: Invalid left-hand side in assignment

Here is what confuses me:

1. Why can we use parentheses as index operator?
2. Is it possible to support using parentheses as index operator, especially as setter, in V8Engine?

[ClearScriptLib]

Hi @ZelgiusLiu,

Why can we use parentheses as index operator?

It's a JScript-specific language extension that facilitates host object access.

JScript and VBScript interact with host objects via IDispatch, an interface that supports parameterized properties and other features not found in JavaScript. JScript's designers apparently felt that parameterized properties were important enough to warrant a JavaScript language extension.

Is it possible to support using parentheses as index operator, especially as setter, in V8Engine?

V8 supports only standard JavaScript language features. It's an open-source project, so modifications are certainly possible, but this sort of change is outside the scope of the ClearScript project.

.NET does have support for parameterized properties, although in C# it's limited to indexers. ClearScript allows standard JavaScript code to access such properties via the following somewhat clunky pattern:

value = obj.Item.get(arg1, arg2, ...); // OR: value = obj.Item(arg1, arg2, ...);
obj.Item.set(arg1, arg2, ..., value);

Here "Item" is the name of the property. Most C# indexers are actually named "Item" under the covers, but other languages may use different names.

Good luck!