Last active
December 9, 2023 12:52
-
-
Save olmokramer/82ccce673f86db7cda5e to your computer and use it in GitHub Desktop.
Regex for CSS colors: hex, rgb(a), hsl(a)
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
/(#([0-9a-f]{3}){1,2}|(rgba|hsla)\(\d{1,3}%?(,\s?\d{1,3}%?){2},\s?(1|0?\.\d+)\)|(rgb|hsl)\(\d{1,3}%?(,\s?\d{1,3}%?\)){2})/i |
none keyword allowed in latest syntax (while values are space seprated not comma separated ) hen how to capture these
following are valid css
- rgb(none 10 20)
- hsl(120deg none none)
- hwb(200 none 0.5)
Here's the regular expression I've got. It recognizes hex-colors and simple color functions. I'm using it in a remarkjs
plugin to add color squares next to colors, similar to how GitHub does this: #4F82A9
. It might be a bit too big, but it runs on the server for me, so it's fine.
/^(#[0-9a-fA-F]{3,4}|#[0-9a-fA-F]{6}|#[0-9a-fA-F]{8}|rgb\(\s*\d*(?:\.\d*)?\s*,\s*\d*(?:\.\d*)?\s*,\s*\d*(?:\.\d*)?\s*\)|rgba\(\s*(?:\d*(?:\.\d*)?%|0)\s*,\s*(?:\d*(?:\.\d*)?%|0)\s*,\s*(?:\d*(?:\.\d*)?%|0)\s*,\s*\d*(?:\.\d*)?%?\s*\)|rgba?\(\s*\d*(?:\.\d*)?\s*\d*(?:\.\d*)?\s*\d*(?:\.\d*)?\s*(?:\/\s*\d*(?:\.\d*)?%?\s*)?\)|rgba?\(\s*(?:\d*(?:\.\d*)?%|0)\s*(?:\d*(?:\.\d*)?%|0)\s*(?:\d*(?:\.\d*)?%|0)\s*(?:\/\s*\d*(?:\.\d*)?%?\s*)?\)|hsl\(\s*\d*(?:\.\d*)?(?:deg|grad|rad|turn)?\s*,\d*(?:\.\d*)?%\s*,\s*\d*(?:\.\d*)?%\s*\)|hsla\(\s*\d*(?:\.\d*)?(?:deg|grad|rad|turn)?\s*,(?:\d*(?:\.\d*)?%|0)\s*,\s*(?:\d*(?:\.\d*)?%|0)\s*,\s*\d*(?:\.\d*)?%?\s*\)|h(?:sla?|wb)\(\s*\d*(?:\.\d*)?(?:deg|grad|rad|turn)?\s*\d*(?:\.\d*)?\s*\d*(?:\.\d*)?\s*(?:\/\s*\d*(?:\.\d*)?\s*)?\)|h(?:sla?|wb)\(\s*\d*(?:\.\d*)?(?:deg|grad|rad|turn)?\s*(?:\d*(?:\.\d*)?%|0)\s*(?:\d*(?:\.\d*)?%|0)\s*(?:\/\s*\d*(?:\.\d*)?%?\s*)?\))$/
And I'm constructing it like this (JavaScript):
const num = String.raw`\d*(?:\.\d*)?`;
const hue = `${num}(?:deg|grad|rad|turn)?`;
const colorFuncs = [
// Hex colors: #000, #0000, #000000, #00000000
`#[0-9a-fA-F]{3,4}`,
`#[0-9a-fA-F]{6}`,
`#[0-9a-fA-F]{8}`,
// Legacy rgb/rgba: rgb(1,2,3), rgba(1,2,3,4)
String.raw`rgb\(\s*${num}\s*,\s*${num}\s*,\s*${num}\s*\)`,
String.raw`rgba\(\s*(?:${num}%|0)\s*,\s*(?:${num}%|0)\s*,\s*(?:${num}%|0)\s*,\s*${num}%?\s*\)`,
// Modern rgb/rgba: rgba(1 2 3 / 0.5)
String.raw`rgba?\(\s*${num}\s*${num}\s*${num}\s*(?:/\s*${num}%?\s*)?\)`,
String.raw`rgba?\(\s*(?:${num}%|0)\s*(?:${num}%|0)\s*(?:${num}%|0)\s*(?:/\s*${num}%?\s*)?\)`,
// Legacy hsl/hsla: hsl(1deg,2%,3%)
String.raw`hsl\(\s*${hue}\s*,${num}%\s*,\s*${num}%\s*\)`,
String.raw`hsla\(\s*${hue}\s*,(?:${num}%|0)\s*,\s*(?:${num}%|0)\s*,\s*${num}%?\s*\)`,
// Modern hsl/hsla/hwb: hsla(1deg 2% 3% / 0.5)
String.raw`h(?:sla?|wb)\(\s*${hue}\s*${num}\s*${num}\s*(?:/\s*${num}\s*)?\)`,
String.raw`h(?:sla?|wb)\(\s*${hue}\s*(?:${num}%|0)\s*(?:${num}%|0)\s*(?:/\s*${num}%?\s*)?\)`,
];
export const ColorRegex = new RegExp(`^(${colorFuncs.join("|")})$`);
Here's what this regex doesn't recognize: lab()
, lch()
, oklab()
, oklch()
, color()
, none
keyword, <system-color>
type, transparent
, currentColor
and named colors. Feel free to extend on this one, I'm not planning to, since for my use case I don't need that much specificity.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Also I would like to point out that in general, a single regex that captures all possible values across all color spaces, hex, named colors, etc. is difficult to formulate especially if:
It is still better to test the color string against different specialized patterns to determine which one matches (if any).