Call Unity function from inside .jslib javascript function in Webgl

Is it possible to call a function in Unity from within the .jslib file? Something like this:

var loadFromUrlPlugin = {

    loadDataFromUrl: function(link){

        var url = Pointer_stringifyl(link);

                //Will this work?
                gameContainer.SendMessage('JsListener', 'SetBodyFromText', text);

mergeInto(LibraryManager.library, loadFromUrlPlugin);

By doing a console.log(SendMessage) from within the .jslib, I could see it was defined. Therefore, though I haven’t checked the precise example from my question, something like it should work. Just remove the ‘gameContainer’ part and call SendMessage directly.