求高手解释一段js代码，作用是背景横向滚动

var scrollSpeed = 70;
var step = 1;
var current = 0;
var imageWidth = 2247;
var headerWidth = 800;
var restartPosition = -(imageWidth - headerWidth);function scrollBg(){current -= step;if (current == restartPosition){current = 0;}$('body').css("background-position",current+"px 0");}
var init = setInterval("scrollBg()", scrollSpeed);

答案：jquery?好像scrollBg()不用双引号吧，var init = setInterval("scrollBg()", scrollSpeed);也可以改成 var init = setInterval(function(){scrollBg();}, scrollSpeed);

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