如何从Swift调用JavaScript

Question

I would like to extend my spreadsheet app with some user-defined macros. It seems to be a good idea to use javascript ...

It found a "small issue" (I am very unfamiliar with javascript at all)

import JavaScriptCore

let context = JSContext()!
context.exceptionHandler = { context, exception in
    print("exception:", exception?.toString() ?? "")
}

context.evaluateScript(
    """
    foo = function(a, b) {
        return a + b
    }
    """
)
context.evaluateScript("foo(1, 2)") // 3
context.objectForKeyedSubscript("foo")?.call(withArguments: [1,2]) // 3

context.evaluateScript(
    """
    Foo = function() {}
    Foo.foo = function(a, b) {
        return a + b
    }
    """
)
context.evaluateScript("Foo.foo(1, 2)") // 3

// exception.  TypeError: undefined is not an object
context.objectForKeyedSubscript("Foo.foo")?.call(withArguments: [1, 2]) // Foo.foo is undefined ?????

If Foo.foo is undefined, how it could run just one line earlier?

Answer 1

finally I found a solution ...

context.objectForKeyedSubscript("Foo")?.objectForKeyedSubscript("foo")?.call(withArguments: [1, 2]) // 3

or better ...

extension JSContext {
    func objectForKeySubscript(_ dotted: String) -> JSValue! {
        var iterator = dotted.split(separator: ".").makeIterator()
        var jsValue = self.objectForKeyedSubscript(iterator.next())
        while let str = iterator.next() {
            jsValue = jsValue?.objectForKeyedSubscript(str)
        }
        return jsValue
    }
}
context.objectForKeySubscript("Foo.foo")?.call(withArguments: [1, 2])

and finaly I found, that

context.evaluateScript("Foo.foo")?.call(withArguments: [1, 2])

works without any trouble ... :-)

Answer 2

You tried .call(withArguments . But I think this works with Function.prototype.call() that requires two arguments(object and arguments). For more info: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call

This works

context.objectForKeyedSubscript("Foo")?.invokeMethod("foo", withArguments: [1, 2])