---
title: "evaluate(inJavaScriptContext:completion:)"
framework: tvmlkit
role: symbol
role_heading: Instance Method
path: "tvmlkit/tvapplicationcontroller/evaluate(injavascriptcontext:completion:)"
---

# evaluate(inJavaScriptContext:completion:)

Evaluates a block in the JavaScript execution queue.

## Declaration

```swift
func evaluate(inJavaScriptContext evaluation: @escaping (JSContext) -> Void, completion: (@Sendable (Bool) -> Void)? = nil)
```

```swift
func evaluate(inJavaScriptContext evaluation: @escaping (JSContext) -> Void) async -> Bool
```

## Parameters

- `evaluation`: The block to be evaluated in the JavaScript execution queue.
- `completion`: The callback after the block has been executed. doc://com.apple.documentation/documentation/Swift/true if the block was evaluated; doc://com.apple.documentation/documentation/Swift/false otherwise.

## Discussion

Discussion important: You can call this method from synchronous code using a completion handler, as shown on this page, or you can call it as an asynchronous method that has the following declaration: func evaluate(inJavaScriptContext evaluation: @escaping (JSContext) -> Void) async -> Bool For information about concurrency and asynchronous code in Swift, see Calling Objective-C APIs Asynchronously. This method adds a block to the JavaScript execution queue and invokes the completion block after the evaluation block has finished execution. The context block parameter is valid within the scope of the evaluation block and should not be referenced by the app outside the block.

## See Also

### Controlling and Handling Events

- [stop()](tvmlkit/tvapplicationcontroller/stop().md)