Better (?) weight matching when desired weight is unavailable

match-weight.js

/* 
 * See www-style
 * @param req: Desired weight. A multiple of 100 in [100-900]
 * @param available: An array of multiples of 100 in [100-900]
 * @return The weight picked or -1 if falling back is better
 * Call like matchWeight(400, [100, 600, 900])
 */
function matchWeight(req, available) {
	if (available.indexOf(req) > -1) {
		return req;
	}
	
	for (o = -100; Math.abs(o) <= 300; o = -o - (o < 0? 0 : 100)) {
		if (available.indexOf(req + o) > -1) {
			return req + o;
		}
	}
	
	return -1;
}