isDark.js

isDark.js is the smallest code to know if any color is dark or light. 553 bytes gzipped // 773 bytes minified. No dependency and crossbrowser (IE9+). Will be adapted for Node.JS.

isDark.js supports every color :

• HSL() and HSLA()
• RGB() and RGBA() (including with percentage values)
• Hexadecimal (#RGB, #RGBA, #RRGGBB and #RRGGBBAA)
• Every keyname, including rebeccapurple and transparent (return both true)

isDark.js, however, don't detect illegal and deprecated values. It doesn't support currentColor.

How to use

Just call window.isDark("black") // true.

Examples

isDark("black");
isDark("white");
isDark("salmon");
isDark("rgb(200 24 37)");
isDark("rgba(200, 24, 37)");
isDark("rgb(0% 0% 0%)");
isDark("hsl(0 50% 100%)");
isDark("hsla(0, 50%, 100%, 1)");
isDark("#FFF");
isDark("FFF");
isDark("#FF0000");
isDark("FF000000");

isLight()

function isLight(color){
    return !isDark(color);
}

Ressources

About colors and brightness :

• Calculating the Perceived Brightness of a Color (NbdTech)
• Techniques For Accessibility Evaluation And Repair Tools (W3C)
• CSS4 Color Module Level 4 (W3C)

About conversion (all conversion functions were modified) :

• Converting HSL to RGB
• One-liner Hex to RGB
• Short Hex to long hex