<p>In Notepad++, I was writing a JavaScript file and something didn't work: an alert had to be shown when a button was clicked, but it wasn't working.</p>

<p>I has used the auto-complete plugin provided with Notepad++, which presented me with <code>onClick</code>.</p>

<p>When I changed the capital <code>C</code> to a small <code>c</code>, it did work.</p>

<p>So first of all, when looking at the functions in the auto-completion, I noticed a lot of functions using capitals.</p>

<p>But when you change <code>getElementById</code> to <code>getelementbyid</code>, you also get an error, and to make matters worse, my handbook from school writes all the stuff with capital letters but the solutions are all done in small letters.</p>

<p>So what is it with JavaScript and its selective nature towards which functions can have capital letters in them and which can't?</p>

Javascript is
ALWAYS
case-sensitive, html is not.
It sounds as thought you are talking about whether html attributes (e.g. onclick) are or are not case-sensitive.  The answer is that the attributes are not case sensitive, but the way that we access them through the DOM is. 
So, you can do this:
```
```
<div id='divYo' onClick="alert('yo!');">Say Yo</div> // Upper-case 'C'
```
```
or:
```
```
<div id='divYo' onclick="alert('yo!');">Say Yo</div> // Lower-case 'C'
```
```
but through the DOM you must use the correct case. So this works:
```
```
getElementById('divYo').onclick = function() { alert('yo!'); }; // Lower-case 'C'
```
```
but you cannot do this:
```
```
getElementById('divYo').onClick = function() { alert('yo!'); }; // Upper-case 'C'
```
```
EDIT: CMS makes a great point that most DOM methods and properties are in
camelCase
.  The one exception that comes to mind are event handler properties and these are generally accepted to be
the wrong way to attach to events
anyway. Prefer using
```
addEventListener
```
as in:
```
```
document.getElementById('divYo').addEventListener('click', modifyText, false);
```
```