我想點(diǎn)擊按鈕，改變<p>標(biāo)簽內(nèi)的文本內(nèi)容，可是總是提示：Uncaught TypeError: Cannot read property 'nodeValue' of undefined/////////html/////////// <input?type="text"?name="email"?id="email"?placeholder="請輸入郵箱"> <button?id="check-email">郵箱格式是否符合</button> <div?class="email-result">請點(diǎn)擊查詢</div> /////////////js//////////// function?isEmail(emailStr)?{ ????var?emailResult?=?document.getElementsByClassName("email-result"); console.log(typeof?emailResult)????????????//這里輸出object console.log(emailResult.firstChild.nodeValue)?????//未定義 emailResult.firstChild.nodeValue?=?"finish?your?implement";????????//未定義 }