What does “async: false” do in jQuery.ajax()?

Question

Specifically, how does it differ from the default ( async: true ) ?

In what circumstances would I want to explicit set async to fals

Answer 1

One use case is to make an ajax call before the user closes the window or leaves the page. This would be like deleting some temporary records in the database before the user can navigate to another site or closes the browser.

 $(window).unload(
        function(){
            $.ajax({
            url: 'your url',
            global: false,
            type: 'POST',
            data: {},
            async: false, //blocks window close
            success: function() {}
        });
    });