driver.get("http://www.google.com")
    .then(function() {
        return driver.getCurrentUrl();
    })
    .then(function(currentUrl) {
        // work with the current url of browser
    });

print(api.driver.getCurrentUrl().toString())

要显示，必须使用toString：

var currentURL = driver.getCurrentUrl().toString();
console.log("***>>> getCurrentUrl: "+currentURL);