How CSS resolves conflicts: the specificity rule

cssApril 28, 2020April 28, 2020

There are two main ways of how CSS deals with conflicting rules: specificity and cascading. In this article, we will focus on specificity.

Take the following example:

div p { color: green;}
p { color: red;}

Applied to this HTML:

<body id="home-page" class="blog">
    <div class="intro">
        <p> some content</p>
    </div>
</body>

The cascading rule in CSS will indicate that the paragraph should be reb, given the last rule. However, we will see that the paragraph is green. And that is because of the first rule is more specific than the last rule.

ok, but what happens if we have a CSS like this one:

#home-page.blog { color: green;}
.intro .blog p { color: blue; }
#home-page { color: orange;}
body div p { color: red;}

With the HTML being the same, what color will the paragraph be in this case?

How CSS specificity is calculated?

The CSS power can be determined by calculating the sum of all the selectors that are used in that statement. For this we can use the following table:

The most powerful selectors are the ID's (100 specificity points) , followed by classes (10 specificity points), and finally the elements selectors (just 1 specificity points each).

The pseudo-class selectors (for example :hover, :before or :after) and the attributes selectors have the same power as a class selector (10 points).

So, with this knowledge, let's calculate the specificity levels in our example:

#home-page.blog { color: green;}
// one ID and one CLASS
// #home-page(100) + .blog(10)  = 110

.intro .blog p { color: blue; }
// two CLASS and one ELEMENT
// .intro(10) + .blog(10) + p(1) = 21

#home-page { color: orange;}
// one ID 
// #home-page (100) = 100

body div p { color: red;}       
// three elements  
// body(1)  + div(1) + p(1) = 3

So the first rule gets the most specificity power, with 110 points making the text green colored.

Also, keep in mind that specificity is more powerful than cascading. However, if we have conflicting rules, with the same specificity then the result will be determined based on the cascading / order.

Example:

div p { color: green;}
// div (1) + p (1)  = 2

body p { color: blue; }
// body(1) + p (1)  = 2

// same specifity; the last rule wins
// paragraph is blue

What about the specificity of `!important` and inline styles

In normal circumstances, we should avoid as much as possible to use both !important and inline styles. But if we have to, keep in mind that inline styles count as 1000 points, and !important is even more powerful with 10.000 points.

So the full table of specificity points looks like this:

Alright friends, that's all for now! Have a fantastic day 🙂

cssApril 27, 2020

The CSS Grid uses lines to position the elements. By default, we can use line numbers to place the elements.

But if you find notations like .header { grid-column: 1 / 3; } confusing then we can define name for these lines.

The name defining is done in the grid-template-columns (and, if needed, in the grid-template-rows):

.container {
    display: grid;
    grid-template-columns: [article-start] 2fr [picture-start] 1fr [nav-start] 80px [nav-end];
}

So now we can say:

.header {
    grid-column: article-start / nav-start;
}
.article {
    grid-column: article-start/picture-start;
}
.picture {
    grid-column: picture-start / nav-start;
}
.navigation {
    grid-column: nav-start / nav-end;
}

Check out below the full working example.

See the Pen
Using names for CSS grid lines by JS Craft (@js-craft)
on CodePen.

Defining multiple names for the same lines

But wait, there is more! We can define more that one name for a line.

It would be cool to define our article with something like article-start to article-end.

However, the article-end will be the starting point for the picture section. This means that we will then have to write for the picture: grid-row: article-end / nav-start; instead of an ideal grid-row: picture-start / picture-end;

In most cases, the ending point for something is the starting point for something else. So, therefore, the need to have multiple names for the same line.

We can implement this by just adding an extra name in the square brackets.

.container {
  grid-template-columns: 
      [article-start] 
      2fr 
      [article-end picture-start] 
      1fr 
      [picture-end nav-start] 
      80px 
      [nav-end];
}

So that we can now say:

.picture {
    grid-row: picture-start / picture-end;
}

Check out here the codepen with multiple names for the same lines. Cheers!

cssApril 22, 2020

Let's say we have a layout made of 10 equal-width columns. Then the container element will look like this:

.container {
    grid-template-columns: 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr;
}

It's a bit troublesome to write a line where you paste ten times the same 1fr. Imagine how fun it's to read this line. Luckily we have the repeat function for situations like this one.

.container {
    grid-template-columns: repeat(10, 1fr);
}

A big readability improvement. You tell the function how many times to repeat, and what to repeat.

If works for both the grid-template-columns and grid-template-rows.

We can give it also a pattern to repeat:

.container {
    grid-template-columns: repeat(3, 1fr 50px);
    // it will create 6 columns
    // 1fr 50px 1fr 50px 1fr 50px 
}

Using the CSS grid repeat function with named lines

And we can even use it with named lines.

.container {
    grid-template-columns: repeat(3, [col-start ] 1fr [col-end] );
    // it will create 3 columns
    // [cstart ] 1fr  [cend] [cstart ] 1fr  [cend]  [cstart ] 1fr  [cend] 
}

Given the fact that we will have the same name for the columns, we will need to a second parameter in the grid-column to indicate instance number of the name we want to place an element:

.my-element {
    grid-column: cstart 2 / cend 2;
}

Using the repeat function with auto-fill

But what if we want to have a layout where we want to have as many columns of 200px as they fit in the width of the container? Well, for this we can use the auto-fill:

.container {
    grid-template-columns: repeat( auto-fill , 200px );
    // it will  make as many 200px columns as possible 
    // eq: your screen is 1500px , it will make 7 columns
}

And that's all for now, folks! Have a fantastic day!

cssApril 21, 2020April 20, 2020

Some days ago I have written a short intro to the attribute selector in CSS. I have found out two new tricks for this selector that I want to share with you today.

Case-insensitive CSS attribute selectors

First, the attribute selector is case sensitive. This can be especially troublesome for the data- attributes.

Take for example the following set of tags:

<div data-status="OPEN">First widget</div>
<div data-status="open">Second widget</div>
<div data-status="open">Third widget</div>

Give the case sensitivity the following selector will target only the first div.

// will target only the first div
div[data-status="OPEN"] { color: red;}

But, we have the i flag in the attribute selector. And with it, we can target tags no matter the capitalization.

// will target all the divs
div[data-status="OPEN" i] { color: red;}

Pay atattion to the fact that the i flag will not work in IE.

CSS attribute selector for multiple tags

The second trick is the ability to target tags based on multiple attributes.

For example, if we want to target all the h1 tags that have both a rel="main subject" and a title="important note":

<h1 rel="main subject" title="important note">Multiple Attributes</h1>

Then we can write

h1[rel="main subject"][title^="important note"] { 
    color: red; 
}

Learned this one from the excellent CSS Tricks article: The Skinny on CSS Attribute Selectors.

cssApril 20, 2020

cssApril 14, 2020

cssApril 13, 2020July 8, 2020

What if I told you that you only need to know only 3 CSS properties to make a fully responsive CSS grid like the one below:

Let's start with the HTML layout. Just a container and the divs corresponding to the articles and header + footer:

<div class="container">
  <div class="header">Header</div>
  <div class="art first">Article 1</div>
  <div class="art second">Article 2</div>
  <div class="art third">Article 3</div>
  <div class="footer">Footer</div>
</div>

First, we will need to set up our container to grid and add a bit of gap between the cells :

.container {
  display: grid;
  grid-gap: 10px;
}

The most important part is made of defining the actual grid. If we would put this layout in an Excell table, it would look like this:

This can be translated into CSS by using the grid-template-areas property:

.container {
 grid-template-areas: 
    "h  h  h"
    "a1 a2 a3"
    "f  f  f"; 
  display: grid;
  grid-gap: 10px;
}

And now to place the HTML elements in the corresponding CSS grid cell we can use the grid-area prop:

.header { grid-area: h; }
.art.first { grid-area: a1; }
.art.second { grid-area: a2; }
.art.third { grid-area: a3; }
.footer { grid-area: f; }

Making the CSS grid responsive

In order to make this one responsive, we can just change the table layout:

So a media query to and again grid-template-areas to the rescue.

@media only screen and (max-width: 600px) {
  .container {
    grid-template-areas: 
        "h"
        "a1"
        "a2"
        "a3"
        "f";
  }
}

We could have also used the display:block, but the idea is just to show how flexible and useful grid-template-areas can be to manage our layout configurations.

And that's all folks! Just 3 properties (grid-area, grid-gap and grid-template-areas ) to make a fully responsive CSS Grid layout.

You can see below the full working codepen for this example. Cheers!

See the Pen
Simple CSS Grid by JS Craft (@js-craft)
on CodePen.

cssApril 9, 2020

cssApril 7, 2020

Let's say we have the following set of rules in a CSS file:

.red {
    color: red;
}

.blue {
    color: blue;
}

.green {
    color: green;
}

And the following tags in our HTML:

<div class="red green blue"> First div.</div>
<div class="blue red green"> Second div.</div>
<div class="green blue red"> Third div.</div>

The question is: what color will we have for these divs? Stop for a few seconds and try to answer the question.

The correct answer: they’re all green.

The order of the class names in HTML tags has no importance on the styles. The lines class="red green blue", class="blue red green" or class="green blue red" are the same thing.

All 3 selectors have the same specificity (just a simple class selector). And given that .green comes later in the stylesheet, it will override the .red and .blue selectors.

Therefore all the divs will have the color green. Cascading wins again.

By the way, this can make a great CSS interview question 🙂

cssApril 6, 2020

Take the following example. We have a link, followed by a few words. And we want a 20px margin space between the link and the text.

.container {
    border: 1px solid black;
    display: float;
    padding: 5px;
}

a {
    margin-right: 20px; 
    background-color: yellow;
}

A link

some text

In this content adding a margin-right: 20px; makes perfect sense.

But what if the flex-direction of the container changes in reverse? Or the user is using a translation extension? Arabic is read right to left.

Then our element will look like this:

A link

some text

The margin will still be on the right side, and we will have to add some more lines of code to make it work again.

Meet the CSS logical properties. We can replace the plain old margin with margin-inline-start: 20px;.

a {
    margin-inline-start: 20px; 
}

What it does is instead of saying "add a margin to the right”, we will have “regardless of direction, put a margin on the starting side”. It does not matter if the starting side is on the left or the right.

A link

some text

Pretty cool, no? 🙂

If we want to replace some other margins, we can use the following table of correspondence:

margin-top      -> margin-block-start
margin-left     -> margin-inline-start
margin-right        -> margin-inline-end
margin-bottom   -> margin-block-end

And it works also with border and padding.

How CSS specificity is calculated?

What about the specificity of !important and inline styles

Defining multiple names for the same lines

Using the CSS grid repeat function with named lines

Using the repeat function with auto-fill

Case-insensitive CSS attribute selectors

CSS attribute selector for multiple tags

Making the CSS grid responsive

What about the specificity of `!important` and inline styles