【JS】deliver parameter in setInterval and setTimeout fun

    function scroll(img_list, img_num) {
        var content = $(img_list);
        var w = content.find('li').outerWidth(true);
        content.animate({"margin-left": parseInt(-w*this_index)});
            this_index++;
            if(this_index >= img_num)
                this_index = 0; 
        console.log(w);
    } 
    setInterval(function() {
　　　　　scroll(".imgarea", 3);
　　}, 2000); 

　　this is wrong 

setInterval(scroll(".imgarea", 3), 2000);　　//wrong

     you can change to this ,using anonymous function 

setInterval(function() {　　//right
　　scroll(".imgarea", 3);

}, 2000);  

　it confused me for a longtime ,i always think my function made same mistake ,but after lot of tests and debug , i found there was something wrong with setInterval function .Remember this !

————★ From Laker's blog ★

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Fighting and insisting~