function bnModPow()

in MultiRegion/2_UI/src/assets/js/aws/amazon-cognito-identity.js [1105:1179]
69 lines of code
19 McCabe index (conditional complexity)

	function bnModPow(e, m) {
	  var i = e.bitLength(),
	      k,
	      r = nbv(1),
	      z = new Montgomery(m);
	  if (i <= 0) return r;else if (i < 18) k = 1;else if (i < 48) k = 3;else if (i < 144) k = 4;else if (i < 768) k = 5;else k = 6;

	  // precomputation
	  var g = new Array(),
	      n = 3,
	      k1 = k - 1,
	      km = (1 << k) - 1;
	  g[1] = z.convert(this);
	  if (k > 1) {
	    var g2 = nbi();
	    z.sqrTo(g[1], g2);
	    while (n <= km) {
	      g[n] = nbi();
	      z.mulTo(g2, g[n - 2], g[n]);
	      n += 2;
	    }
	  }

	  var j = e.t - 1,
	      w,
	      is1 = true,
	      r2 = nbi(),
	      t;
	  i = nbits(e[j]) - 1;
	  while (j >= 0) {
	    if (i >= k1) w = e[j] >> i - k1 & km;else {
	      w = (e[j] & (1 << i + 1) - 1) << k1 - i;
	      if (j > 0) w |= e[j - 1] >> this.DB + i - k1;
	    }

	    n = k;
	    while ((w & 1) == 0) {
	      w >>= 1;
	      --n;
	    }
	    if ((i -= n) < 0) {
	      i += this.DB;
	      --j;
	    }
	    if (is1) {
	      // ret == 1, don't bother squaring or multiplying it
	      g[w].copyTo(r);
	      is1 = false;
	    } else {
	      while (n > 1) {
	        z.sqrTo(r, r2);
	        z.sqrTo(r2, r);
	        n -= 2;
	      }
	      if (n > 0) z.sqrTo(r, r2);else {
	        t = r;
	        r = r2;
	        r2 = t;
	      }
	      z.mulTo(r2, g[w], r);
	    }

	    while (j >= 0 && (e[j] & 1 << i) == 0) {
	      z.sqrTo(r, r2);
	      t = r;
	      r = r2;
	      r2 = t;
	      if (--i < 0) {
	        i = this.DB - 1;
	        --j;
	      }
	    }
	  }
	  return z.revert(r);
	}