function readBitField(bits, bitIndex) {
	var bitLen = 8 * (bits.length - 1) - bits[0];
	var setBits = {};
	for (var i = 0; i < bitLen; ++i) {
		var byteN = 1 + Math.floor(i / 8);
		var bit = 7 - (i % 8);
		var mask = 1 << bit;
		var bitVal = ((bits[byteN] & mask) !== 0);
		var name = bitIndex[i];
		if (bitVal && typeof (name) === 'string') {
			setBits[name] = true;
		}
	}
	return (Object.keys(setBits));
}
Add custom format
@this   Ajv
@param {String} name format name
@param {String|RegExp|Function} format string is converted to RegExp; function should return boolean (true when valid)
@return {Ajv} this for method chaining