我用這個(gè)很多年了：function findFirstChildByClass(element, className) {    var foundElement = null, found;    function recurse(element, className, found) {        for (var i = 0; i < element.childNodes.length && !found; i++) {            var el = element.childNodes[i];            var classes = el.className != undefined? el.className.split(" ") : [];            for (var j = 0, jl = classes.length; j < jl; j++) {                if (classes[j] == className) {                    found = true;                    foundElement = element.childNodes[i];                    break;                }            }            if(found)                break;            recurse(element.childNodes[i], className, found);        }    }    recurse(element, className, false);    return foundElement;}但突然，這一行拋出了一個(gè)錯(cuò)誤：var classes = el.className != undefined? el.className.split(" ") : [];未捕獲的類型錯(cuò)誤：el.className.split 不是函數(shù)我現(xiàn)在看不出出了什么問(wèn)題。