querying.js

var isTag = require("domelementtype").isTag;

module.exports = {
	filter: filter,
	find: find,
	findOneChild: findOneChild,
	findOne: findOne,
	existsOne: existsOne,
	findAll: findAll
};

function filter(test, element, recurse, limit){
	if(!Array.isArray(element)) element = [element];

	if(typeof limit !== "number" || !isFinite(limit)){
		limit = Infinity;
	}
	return find(test, element, recurse !== false, limit);
}

function find(test, elems, recurse, limit){
	var result = [], childs;

	for(var i = 0, j = elems.length; i < j; i++){
		if(test(elems[i])){
			result.push(elems[i]);
			if(--limit <= 0) break;
		}

		childs = elems[i].children;
		if(recurse && childs && childs.length > 0){
			childs = find(test, childs, recurse, limit);
			result = result.concat(childs);
			limit -= childs.length;
			if(limit <= 0) break;
		}
	}

	return result;
}

function findOneChild(test, elems){
	for(var i = 0, l = elems.length; i < l; i++){
		if(test(elems[i])) return elems[i];
	}

	return null;
}

function findOne(test, elems){
	var elem = null;

	for(var i = 0, l = elems.length; i < l && !elem; i++){
		if(!isTag(elems[i])){
			continue;
		} else if(test(elems[i])){
			elem = elems[i];
		} else if(elems[i].children.length > 0){
			elem = findOne(test, elems[i].children);
		}
	}

	return elem;
}

function existsOne(test, elems){
	for(var i = 0, l = elems.length; i < l; i++){
		if(
			isTag(elems[i]) && (
				test(elems[i]) || (
					elems[i].children.length > 0 &&
					existsOne(test, elems[i].children)
				)
			)
		){
			return true;
		}
	}

	return false;
}

function findAll(test, elems){
	var result = [];
	for(var i = 0, j = elems.length; i < j; i++){
		if(!isTag(elems[i])) continue;
		if(test(elems[i])) result.push(elems[i]);

		if(elems[i].children.length > 0){
			result = result.concat(findAll(test, elems[i].children));
		}
	}
	return result;
}