兼容ie5-ie11及其他主流浏览器的js document.getElementsByClassName 方法

var getElementsByClassName = function(searchClass,node,tag) {
    if(document.getElementsByClassName){
        return  document.getElementsByClassName(searchClass)
    }else{    
        node = node || document;
        tag = tag || ‘*‘;
        var returnElements = []
var els =  (tag === "*" && node.all)? node.all : node.getElementsByTagName(tag);
        var i = els.length;
        searchClass = searchClass.replace(/\-/g, "\\-");
        var pattern = new RegExp("(^|\\s)"+searchClass+"(\\s|$)");
        while(--i >= 0){
            if (pattern.test(els[i].className) ) {
                returnElements.push(els[i]);
            }
        }
        return returnElements;
    }
}
//调用方法
var shiToolBox=document.getElementsByClassName("aaa");