get children of a parent element by tag name

getChildrenByTag.js

/*!
 * get children of a parent element by tag name
 * no fallback to document if parent fail
 * gist.github.com/englishextra/6d843e16c49cfde0a394bd9d76383b13
 * jsfiddle.net/englishextra/c2vr5gxd/
 * jsbin.com/xavocu/edit?html,js,output
 */
getChildrenByTag = (function (d, m) {
	function g(t, p, o) {
		o = Object.create(g.fn);
		/*!
		 * no fallback to document if parent fail
		 */
		/* var f = (function (t, p) {return p ? p[m](t) : []}(t, p)); */
		/*!
		 * this will fallback to document if parent fail
		 */
		var f = (function (t, p) {if(null===p||"undefined"===typeof p)p=document||[];return p[m](t)||[];}(t, p));
		if (t) {
			o.push.apply(o, f);
		}
		return o;
	}
	g.fn = [];
	g.one = function (t, p) {
		return g(t, p)[0] || null;
	};
	return g;
})(document, "getElementsByTagName");


var a = getChildrenByTag("p",document.querySelector("body > div"));
var b = getChildrenByTag.one("p",document.querySelector("body > div"));
alert(a.length);
/*!
 * what kinds of data can be considered empty:
 * undefined or null
 * a zero-length string
 * an array with no members
 * an object with no enumerable properties
 */
alert(b);