isVisible() for Salesforce Classic

Returns true if the softphone is visible or false if the softphone is hidden.

Name	Type	Description
`callback`	function	JavaScript method executed when the API method call is completed.

Name	Type	Description
`result`	boolean	`true` if the softphone is visible, `false` if the softphone isn’t visible.
`error`	string	If the API call was successful, this variable is undefined. If the API call failed, this variable returns an error message.