@codegouvfr/react-dsfr/src/tools/threeDigitColorHexToSixDigitsColorHex.ts

French State Design System React integration library

export function threeDigitColorHexToSixDigitsColorHex(threeDigitColorHex: string) {
    let v, w;
    v = parseInt(threeDigitColorHex, 16); // in rrggbb
    if (threeDigitColorHex.length == 3) {
        // nybble colors - fix to hex colors
        //  0x00000rgb              -> 0x000r0g0b
        //  0x000r0g0b | 0x00r0g0b0 -> 0x00rrggbb
        w = ((v & 0xf00) << 8) | ((v & 0x0f0) << 4) | (v & 0x00f);
        v = w | (w << 4);
    }
    return v.toString(16).toUpperCase();
}