FM / nth-check

/var/www/cobraambalaj/node_modules/nth-check/

/var/www/cobraambalaj/node_modules/nth-check

Name	Size	Mode	Actions
compile.js	1133	0644	edit dl rm
index.js	220	0644	edit dl rm
LICENSE	1260	0644	edit dl rm
package.json	1433	0644	edit dl rm
parse.js	839	0644	edit dl rm
README.md	1454	0644	edit dl rm

Edit: /var/www/cobraambalaj/node_modules/nth-check/compile.js (1133B)

module.exports = compile;

var BaseFuncs = require("boolbase"),
    trueFunc  = BaseFuncs.trueFunc,
    falseFunc = BaseFuncs.falseFunc;

/*
	returns a function that checks if an elements index matches the given rule
	highly optimized to return the fastest solution
*/
function compile(parsed){
	var a = parsed[0],
	    b = parsed[1] - 1;

//when b <= 0, a*n won't be possible for any matches when a < 0
	//besides, the specification says that no element is matched when a and b are 0
	if(b < 0 && a <= 0) return falseFunc;

//when a is in the range -1..1, it matches any element (so only b is checked)
	if(a ===-1) return function(pos){ return pos <= b; };
	if(a === 0) return function(pos){ return pos === b; };
	//when b <= 0 and a === 1, they match any element
	if(a === 1) return b < 0 ? trueFunc : function(pos){ return pos >= b; };

//when a > 0, modulo can be used to check if there is a match
	var bMod = b % a;
	if(bMod < 0) bMod += a;

if(a > 1){
		return function(pos){
			return pos >= b && pos % a === bMod;
		};
	}

a *= -1; //make `a` positive

return function(pos){
		return pos <= b && pos % a === bMod;
	};
}

cmd: