FF.prime = function()

in src/ff.js [1159:1221]
50 lines of code
11 McCabe index (conditional complexity)

    FF.prime = function(p, rng) {
        var n = p.length,
            s = 0,
            loop,
            d = new FF(n),
            x = new FF(n),
            unity = new FF(n),
            nm1 = new FF(n),
            sf = 4849845, /* 3*5*.. *19 */
            i, j;

        p.norm();

        if (p.cfactor(sf)) {
            return false;
        }

        unity.one();
        nm1.copy(p);
        nm1.sub(unity);
        nm1.norm();
        d.copy(nm1);

        while (d.parity() === 0) {
            d.shr();
            s++;
        }

        if (s === 0) {
            return false;
        }

        for (i = 0; i < 10; i++) {
            x.randomnum(p, rng);
            x.pow(d, p);

            if (FF.comp(x, unity) === 0 || FF.comp(x, nm1) === 0) {
                continue;
            }

            loop = false;

            for (j = 1; j < s; j++) {
                x.power(2, p);

                if (FF.comp(x, unity) === 0) {
                    return false;
                }

                if (FF.comp(x, nm1) === 0) {
                    loop = true;
                    break;
                }
            }
            if (loop) {
                continue;
            }

            return false;
        }

        return true;
    };