未捕获的TypeError：undefined不是函数-不是JQuery

Question

I feel terrible for submitting another Uncaught TypeError: undefined is not a function question. But after reading about 20 different answers to these types of questions, either I am missing the point, or the problem was different in those cases.

I have a form with two radio buttons. When one is clicked I want it to change the innerHTML of a <tr></tr> tag.

Here is my JFiddle .

The HTML:

<form name="myForm" autocomplete="off" action="index.php" method="post" enctype="multipart/form-data">
<label for="mode">Text</label>
<input type="radio" name="mode" value="text" id="setText" />
<label for="mode">Image</label>
<input type="radio" name="mode" value="img" id="setImg" />
<table>
<tr id="headerInput"></tr>
</table>
</form>

The Javascript:

document.getElementById("setText").addEventListener("click", function () {
window.getElementById("headerInput").innerHTML = '<td>Title</td><td><input type="text" name="title" value="Hello" /></td>';
});
document.getElementById("setImg").addEventListener("click", function () {
window.getElementById("headerInput").innerHTML = '<td>Banner</td><td><input type="file" name="banner" /></td>';
});

I have tried a few different versions of the same thing, like creating named functions, using the onclick="someFunction()" attribute and object.onclick as well. All of them give me the same error. Your help to understand what I am doing is greatly appreciated.

Answer 1

window.getElementById() isn't defined normally in a browser.

Looking up property 'getElementById' on window returns undefined . You're then attempting to invoke undefined , hence Uncaught TypeError: undefined is not a function .

You probably mean to use document there instead.

Answer 2

You should refer document.getElementById() rather than window.getElementById(). Also, changing the innerHTML is fine but afaik we should refer to the td inside the tr for any manipulations. That's a best practice.

document.getElementById("headerInput").innerHTML

Working fiddle: http://jsfiddle.net/7fpBg/