AlertifyJS to save input from user in Angular

I am trying to use prompt to get the input from the user but not sure how.

in alertify service I have:

getFolder()
{
    alertify.prompt("Enter Folder Name:",
    function(evt:any, value:any ){
      alertify.success('Ok: ' + value);
    },
    function(){
      alertify.error('Cancel');
    });
}

and in mt ts file I run it:

this.alert.getFolder();

The dialog is preset but it is not doing anything if I press OK but if i press cancel it says cancel. I want to save the data to variable in ts file if pressed OK.

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