为输入控件获取未定义的值
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在下面的html和javascript代码（代码笔-https://codepen.io/manuchadha/pen/OJVXdzb）中，我希望打印input控件的值，但我得到的值为undefined-filename is undefined。为什么？
<!DOCTYPE html>
<html>
<head>
<title>some title</title>
<script src="jquery/jquery-3.3.1.min.js"></script>
<script src="index.js"></script>
</head>
<body>
<div id="add-more-answer-div">
<div id="answer-filename-div">
<label id="filename-label" for="answer-filename">Name</label>
<input type="text" id="answer-filename" />
<button
type="button"
id="more-answer-button"
onclick="createNewAnswerSection()"
>
Add More Sections
</button>
</div>
</div>
</body>
</html>
function createNewAnswerSection() {
console.log("will create new answer section");
var answerNameControl = $("#answer-filename");
console.log("answer name control is ", answerNameControl);
if (answerNameControl.value === "") {
alert("give a filename to the answer");
} else {
console.log("filename is ", answerNameControl.value);
}
}
答案
请使用answerNameControl.val（）代替answerNameControl.value
另一答案
您应该完全使用val() ！
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="add-more-answer-div">
<div id="answer-filename-div">
<label id="filename-label" for="answer-filename">Name</label>
<input type="text" id="answer-filename">
<button type="button" id="more-answer-button" onclick="createNewAnswerSection()">Add More Sections</button>
</div>
</div>
<script>
function createNewAnswerSection() {
console.log("will create new answer section");
var answerNameControl = $("#answer-filename").val();
console.log("answer name control is ", answerNameControl);
if (answerNameControl === '') {
alert("give a filename to the answer");
} else {
console.log("filename is ", answerNameControl);
}
}
</script>另一答案
您缺少jQuery的语法，您正在使用answerNameControl.value，它不是有效的synatx，而是可以使用$(answerNameControl).val()来获取值您更新的代码如下
<html>
<head>
<title>some title</title>
<script src="jquery/jquery-3.3.1.min.js"></script>
<script src="index.js"></script>
</head>
<body>
<div id="add-more-answer-div">
<div id="answer-filename-div">
<label id="filename-label" for="answer-filename">Name</label>
<input type="text" id="answer-filename">
<button type="button" id="more-answer-button" onclick="createNewAnswerSection()">Add More Sections</button>
</div>
</div>
</body>
</html>
<script>
function createNewAnswerSection(){
console.log("will create new answer section");
var answerNameControl = $("#answer-filename");
console.log("answer name control is ",answerNameControl);
if($(answerNameControl).val() === ''){
alert("give a filename to the answer");
} else {
console.log("filename is ",$(answerNameControl).val());
}
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