CSS Variables | Learning CSS Best Practices - #01

to declare a variable prefix your variable name with two dashes then to use it, use the var() function

/* -- declaring the variable. -- */

--variable_name: variable_value

/* -- accessing the variable. -- */

html {
    font-family: var(--variable_name);
}

Variable Scope | Global or Local ?

Variables can be either scoped globally or locally. declaring your variables inside the :root pseudo-class makes them available in the global scope and available for use throughout ythe stylesheet.

header {
    --bg-color: red;

    /* bg-color is only visisble to all children of the header element */
}

main {
    background: var(--bg-color);

    /* bg-color is undefined. */
}

/* to declare global variables place all variable inside the :root pseudo-class */

:root {
    bg-color: red;
}

header {
    background: var(--bg-color);
}

main {
    background: var(--bg-color);
}

Common Use Cases

One way to use css variables is to save common colors or an entire color pallete which you can then use to style elements.

:root {
   /* -- Use css variables to declare site colors -- */
   --primary-color: black;
   --secondary-color: gray;
   --tetiary-color: white;

   /* -- Color Palettes -- */
   /* -- black color palette */
   --black-clr-plt-1: rgb(0, 0, 0);
   --black-clr-plt-2: rgb(30, 30, 30);
   --black-clr-plt-3: rgb(60, 60, 60);
   --black-clr-plt-4: rgb(90, 90, 90);

   /* -- brown color palette -- */
   --brown-clr-plt-1: rgb(60, 20, 20);
   --brown-clr-plt-2: rgb(90, 30, 30);
   --brown-clr-plt-3: rgb(120, 40, 40);
   --brown-clr-plt-4: rgb(150, 50, 50);
}

/* -- styling -- */
body {
   background: var(--brown-clr-plt-3);
   color: var(--black-color-plt-1);
   border: 1px solid var(--primary-color);
}

Providing Fallback Values

To provide a fallback value in case the variable is undefined, pass the fallback value as a second argument into the var() function.

:root {
   --site-font: 'Raleway';
}

html {
   font-family: var('Raleway', monospace);
}

/* In this example if site-font is undefined, the monospace font is used. */

that's it, you're welcome to follow the journey onwards on my github