var()
Quick Summary for var()
var() CSS function can be used to insert the value of a custom property (sometimes called a "CSS variable") instead of any part of a value of another property.
Code Usage for var()
:root { --main-bg-color: pink; } body { background-color: var(--main-bg-color); } More Details for var()
var()
The var() CSS function can be used to insert the value of a custom property (sometimes called a "CSS variable") instead of any part of a value of another property.
The var() function cannot be used in property names, selectors or anything else besides property values. (Doing so usually produces invalid syntax, or else a value whose meaning has no connection to the variable.)
Syntax
The first argument to the function is the name of the custom property to be substituted. An optional second argument to the function serves as a fallback value. If the custom property referenced by the first argument is invalid, the function uses the second value.
var( <custom-property-name> , <declaration-value>? )
Note: The syntax of the fallback, like that of custom properties, allows commas. For example, var(--foo, red, blue) defines a fallback of red, blue; that is, anything between the first comma and the end of the function is considered a fallback value.
Values
<custom-property-name> A custom property's name represented by an identifier that starts with two dashes. Custom properties are solely for use by authors and users; CSS will never give them a meaning beyond what is presented here.
<declaration-value> The custom property's fallback value, which is used in case the custom property is invalid in the used context. This value may contain any character except some characters with special meaning like newlines, unmatched closing brackets, i.e. ), ], or }, top-level semicolons, or exclamation marks.
Examples
Using a custom property set on :root
:root { --main-bg-color: pink; } body { background-color: var(--main-bg-color); } Custom properties with fallbacks for use when the property has not been set
/* Fallback */ /* In the component's style: */ .component .header { color: var(--header-color, blue); /* header-color isn't set, and so remains blue, the fallback value */ } .component .text { color: var(--text-color, black); } /* In the larger application's style: */ .component { --text-color: #080; } Specifications
| Specification |
|---|
| CSS Custom Properties for Cascading Variables Module Level 1 # using-variables |
See also
env(…) – read‑only environment variables controlled by the user‑agent. Using CSS variables Select your preferred language English (US)EspañolFrançais日本語한국어Português (do Brasil)Русский中文 (简体) Change language
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"Olivia, my eldest daughter, caught measles when she was seven years old. As the illness took its usual course I can remember reading to her often in bed and not feeling particularly alarmed about it. Then one morning, when she was well on the road to recovery, I was sitting on her bed showing her how to fashion little animals out of coloured pipe-cleaners, and when it came to her turn to make one herself, I noticed that her fingers and her mind were not working together and she couldn’t do anything. 'Are you feeling all right?' I asked her. 'I feel all sleepy,' she said. In an hour, she was unconscious. In twelve hours she was dead. The measles had turned into a terrible thing called measles encephalitis and there was nothing the doctors could do to save her. That was...in 1962, but even now, if a child with measles happens to develop the same deadly reaction from measles as Olivia did, there would still be nothing the doctors could do to help her. On the other hand, there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunised against measles. ...I dedicated two of my books to Olivia, the first was ‘James and the Giant Peach’. That was when she was still alive. The second was ‘The BFG’, dedicated to her memory after she had died from measles. You will see her name at the beginning of each of these books. And I know how happy she would be if only she could know that her death had helped to save a good deal of illness and death among other children."
I just checked google books for BFG, and the dedication is there.
https://www.google.com.au/books/edition/_/quybcXrFhCIC?hl=en&gbpv=1
Roald Dahl, 1986
