Am I subclassing my CSS correctly? - css

Question

I am making a set of buttons for my site, and I am in need of some professional insight.
In order to reduce CSS bloat, I want to subclass my buttons for different colors, ex .button.blue .
Will the following incur issues in the future? (assuming I don't make a class of just .blue)
Do I have to use something like .button.button-blue instead?
.button {
display:inline-block;
padding: 9px 18px;
margin: 20px;
text-decoration: none;
font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
font-weight: bold;
text-align: center;
background: #FFE150;
}
.button.blue {
background: #49b8e7;
border:1px solid #54abcf;
border-bottom:1px solid #398fb4;
color:#FFF
text-shadow: 0 1px 0 rgba(255,255,255, 0.5);
}
.header{
height: 50px;
}
.header.blue {
background: blue;
color: #fff;
}

Answer 1

What you have there with the multi-classes will work fine assuming you want them to work like so:
<div class="button blue">
Will use .button and .button.blue
</div>
<div class="button">
Will only use .button
</div>
<div class="header blue">
Will use .header and .header.blue
</div>
<div class="header">
Will only use .header
</div>
<div class="blue">
Will use neither of the .blue declarations because it doesn't contain header or button.
</div>

Answer 2

A selector like .button.blue actually selects for an element with that has both "blue" and "button" as classes, not a class called .button.blue. See http://www.w3.org/TR/CSS21/selector.html#class-html.
You can use the .button.blue style rule you have listed, but you'll need to rearrange your HTML so that you have something like <button type="button" class="button blue"/>. However, you don't really need to have a button class since it being a button (or <input type="submit">, etc.) is enough to use in your selector. You could write a CSS rule that is simply button.blue, input[type=submit].blue{}

Answer 3

Seems like button.blue is enough.
The only difference between the two is if you use <button class="button blue">, or <button class="button button-blue">.
You even don't need to duplicate the painting in blue... You can just do something like this:
.button
{
// button style
}
.header
{
// header style
}
.blue
{
background: blue;
color: #fff;
}
Of course if you add the blue class to each of them. (<div class="header blue">and<button class="button blue">)

Answer 4

Combine the classes applying the color you want to theme.
HTML:
<input type="text" class="text-field-required default" .../>
<select class="autocomplete-drop-down blue">...</select>
<a href="#" class="button-link green" .../>
CSS:
.text-field-required {
//component css theme without colors
}
.default {
//default color css theme for any component
}
.blue {
//blue css theme for any component
}
.green {
//green css theme for any component
}