window.onload=function () {
    imgLocation("container","box");
}
function imgLocation(parent,content) {
    var cparent=document.getElementById("parent");
    var  ccontent=getChildElement(cparent,content);
    var  imgWidth=ccontent[0].clientWidth;
    var cols= Math.floor(document.documentElement.clientWidth/imgWidth);
    cparent.style.cssText="width"+imgWidth*cols+"px";

}
function getChildElement(parent,content)     {
    var contenArr=[];
    var allcontent=parent.getElementsByTagName("*");
    for (var i=0;i<allcontent.length;i++){
        if (allcontent[i].className==content){
            contenArr.push(allcontent[i]);
        }
    }
    return contenArr;
}