Why do we need “var self = this” in classes in Javascript?

Question

Why can\'t we directly use this instead of self in the following example?

function SeatReservation(name, initialMeal) {
    var self =          


        

Answer 1

Based on your example, there is "no" reason for doing this.

There is however, situations where it will help you, although some may frown upon it's usage.

i.e.

$('a.go').click(function(e)
{
    e.preventDefault();
    if(!$(this).hasClass('busy'))
    {
        $(this).addClass('busy');
        $.ajax(
        {
            success : function(resp)
            {
                $(this).removeClass('busy');
            },
            error : function()
            {
                $(this).removeClass('busy');                
            }
        });
    }
});

In the above, $(this) within the success and error callbacks would not reflect to the link you clicked, as the scope has been lost.

To get around this, you would do var self = $(this) i.e.

$('a.go').click(function(e)
{
    e.preventDefault();
    if(!$(this).hasClass('busy'))
    {
        $(this).addClass('busy');
        var btn = $(this);
        $.ajax(
        {
            success : function(resp)
            {
                btn.removeClass('busy');
            },
            error : function()
            {
                btn.removeClass('busy');                
            }
        });
    }
});