let browser = Erik.visit(url: url) { document, error in
    // browse HTML element, click, submit form and more
}

Erik.visit(url: url) { object, error in
    if let e = error {

    } else if let doc = object {
        // HTML Inspection
    }
}

if let url = Erik.currentURL {..}

let browser = Erik()
browser.visitURL...

for link in doc.querySelectorAll("a, link") {
    print(link.text)
    print(link["href"])
}

if let input = doc.querySelectorAll("input[name=\"user\"]").first {
    input["value"] = "Eric"
}

if let form = doc.querySelector("form[id='search']") as? Form {
    form.submit()
}

let javaScriptSource = "console.log("test");"
Erik.evaluate(javaScript:javaScriptSource) { (obj, err) -> Void in
    if let error = err {
        switch error {
            case ErikError.javaScriptError(let message):
            print(message)
            default :
            print("\(error)")
        }
    }
    else if let capturedValue = obj {
        // do something according to result
    }
}

let javaScriptSource = "console.log('test'); var resultErik = 1 + 1;"

Erik.currentContent { (obj, err) -> Void in
    if let error = err {
    }
    else if let document = obj {
       // HTML Inspection
    }
}

let url = NSURL(string:"https://www.google.com")!
let value = "Erik The Phantom of Opera"
// visit
var future: Future<Document, NSError> = Erik.visitFuture(url: url)
// fill input field
future = future.flatMap { document -> Future<Document, NSError> in
    if let input = document.querySelector("input[name='q']") {
        input["value"] = value
    }
    if let form = document.querySelector("form[name=\"f\"]") as? Form {
        form.submit()
    }
    return Erik.currentContentFuture()
}
// finally get final result as success or error
future.onSuccess { document in
    // parse result
}
future.onFailure { error in
    print("\(error)")
}