Use "this" to call a function

Question

When I try to use "this" to call a function, an error occured saying :"this.slideshow_action is not a function". Can you please let me know my fault!?

var class_slider = {
        current_slide: 0, //Starting Slide
        total_slides: 4, //All Slides
        slideshow_action: function(slide_number) {
            $(".slide_text").hide();
            $(".main_navigation_container").removeClass("selected");
            $("#slide_" + slide_number).addClass("selected");
            $("#slide_" + slide_number + "_text").fadeIn("slow");
        },
        slideshow: function() {
            if (this.current_slide === this.total_slides)
                this.current_slide = 0;//Make a new tour
            else
                this.current_slide++;
           this.slideshow_action(this.current_slide);
        },
        reset_timer: function()
        {
            window.clearInterval(this.slideshow_timer);
            this.slideshow_timer = window.setInterval(this.slideshow, 5000);
        },
        icon_action: function(element) {
            this.reset_timer();
            var arr = element.attr("id").split('_'); //Get Last Part of id(slide number)
            this.current_slide = parseInt(arr[1]); //Get slide Number
            this.slideshow_action(this.current_slide);
        }
    };

Answer 1

Use contexts.

setTimeout(function(context){
        context._someMethod();
    }, 5000, this);
}

var timer = setInterval(function(context){
        context._someMethod();
    }, 5000, this);
}