Hacker News userscript that still doesn't entirely work

gistfile1.js

// ==UserScript==
// @name        HackerNewsHacker
// @namespace   kennethrapp1@gmail.com
// @description Hacker New Hacker Hacks Hacker News
// @include     *news.ycombinator.com/*
// @version     1
// @grant       none
// ==/UserScript==


//Returns true if it is a DOM node
function isNode(o){
  return (
    typeof Node === "object" ? o instanceof Node : 
    o && typeof o === "object" && typeof o.nodeType === "number" && typeof o.nodeName==="string"
  );
}

//Returns true if it is a DOM element    
function isElement(o){
  return (
    typeof HTMLElement === "object" ? o instanceof HTMLElement : //DOM2
    o && typeof o === "object" && o !== null && o.nodeType === 1 && typeof o.nodeName==="string"
	);
}


function arrayContains(a, v) {
    for(var i = 0; i < a.length; i++) {
        if(a[i] === v){
        	return true;
        }
    }
    return false;
}

function arrayRemove(arr) {
    var what, a = arguments, L = a.length, ax;
    while (L > 1 && arr.length) {
        what = a[--L];
        while ((ax= arr.indexOf(what)) !== -1) {
            arr.splice(ax, 1);
        }
    }
    return arr;
}

var LocalStorage =  {

	cache: {},

	usage: function(){
		var limit = 2000000;
		var size = JSON.stringify( window.localStorage).length;
		return parseFloat(((size/limit)*100).toPrecision(2)); // return usage
	},

	/* add a new value to an array in local storage. If the 
	array doesn't exist, create it when called. */
	add: function(key, value){
		
		if(window.localStorage.getItem(key) === null){
			var obj =[value];
		}
		else if(obj = JSON.parse(window.localStorage.getItem(key))){  
			if(arrayContains(obj, value) === false){ 
				obj.push(value);
			}
		}
		
		window.localStorage.setItem(key, JSON.stringify(obj));
		this.getAll();
	},

	/* remove a value from a group */
	remove: function(key, value){
		if(obj = window.localStorage.getItem(key)){
			var json = JSON.parse(obj);
			obj = arrayRemove(json, value);			
			window.localStorage.setItem(key, JSON.stringify(obj));
		}
		this.getAll();
	},
	
	get: function(key){
		if((typeof this.cache == 'object') && (key in this.cache)){
			//console.log("is cached");
			return this.cache[key];
		}
		else if(obj = window.localStorage.getItem(key)){
			//console.log("is not cached");
			var json = JSON.parse(obj);
			this.cache[key] = json;
			return json;
		}
	},

	getAll: function(){
		var i = 0, //i is standing for int
		oJson = {}, //o is standing for object
		sKey; //s is standing for string			
		while ((sKey = window.localStorage.key(i))) {
			oJson[sKey] = JSON.parse(window.localStorage.getItem(sKey));
			i++;
		}
		this.cache = oJson;
		return oJson;
	}
}

var HNHacker = {}

HNHacker.Users  = [];
HNHacker.Ignore = [];
HNHacker.States = {};

HNHacker.keys = {
	"following" : "f",
	"ignoring"  : "i"
}

/* do something relative to the passed node and username, based on
	the state, which will be one of the state keys. */
HNHacker.applyUserState = function(state, username, node){
	
	// ignore user - hide their content
	if(arrayContains(state, HNHacker.keys['ignoring'])){
		
		var ignore = HNHacker.MakeElement("div", {
			"id" 	: "ignore_"+username,
			"class"	: "dead"
		}, "[ignored]");

		var target = node.parentNode.parentNode.childNodes[3];
		target.style.visibility	= "hidden";
		target.style.position	= "absolute";
		node.parentNode.parentNode.insertBefore(ignore, node.parentNode.parentNode.childNodes[2]);
	}

}

// run a callback for nodes matching an xpath. 
HNHacker.AffectDOMPath = function(expression, callback){	

	var result = document.evaluate(expression,document,null,XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,null);	

	if(result.snapshotLength){ 
		for(i = 0; i <= result.snapshotLength - 1; i++){
			callback.call(this, result.snapshotItem(i));
		}
	}
}

/* build a generic html element. return the node.*/
HNHacker.MakeElement = function(tag, attrs, inner){
	
	var element = document.createElement(tag);

	if(typeof attrs == 'object'){
		for(var a in attrs){
			element.setAttribute(a, attrs[a]);
		}
	}
	
	if(typeof inner == "string"){
		var b = document.createTextNode(inner);
		element.appendChild(b);
	}
	else if(isElement(inner)){
		element.appendChild(inner);
	}
	
	return element;
}


/* build and return an html link element with a callback for the click event. easy peasy. */
HNHacker.BuildTextControl = function(textcontent, callback, args){

	var control = this.MakeElement("a", {
		"href" 	: "#",
		"class" : "hn_top"
	}, textcontent );

	control.addEventListener('click', function(event){  
		event.preventDefault();
		callback.apply(this, args);
	}, false );	

	return control;
}

/* build a menu. obj is an xpath or node to which the menu will be appended. 
menuItems is an array of arrays - each subarray looks like

[label, callback, [args]]

label is a string (the inner link text) for the control,
callback is a callback for the click event, and args is an
array of arguments to pass to the callback. 
 */
HNHacker.BuildMenu = function(obj, menuItems){

	/* hopefully now this works whether you send a node or xpath expression... */
	if(isElement(obj)){
		obj.appendChild(document.createTextNode(" [ "));
		for (var i = menuItems.length - 1; i >= 0; i--) {
			var control = this.BuildTextControl.apply(this, menuItems[ menuItems.length - (i+1) ]);
			obj.appendChild(control);

			if(i > 0){
				obj.appendChild(document.createTextNode(" | "));
			}
		};
		obj.appendChild(document.createTextNode(" ] "));
	}
	else{
		this.AffectDOMPath(obj, function(item){
			item.appendChild(document.createTextNode(" [ "));
			for (var i = menuItems.length - 1; i >= 0; i--) {
				var control = this.BuildTextControl.apply(this, menuItems[ menuItems.length - (i+1) ]);
				item.appendChild(control);
				if(i > 0){
					item.appendChild(document.createTextNode(" | "));
				}
			};
			item.appendChild(document.createTextNode(" ] "));
		});
	}
}

/********************************************** startup ***********************************************/

/* create the "ui panel" in the blank table row right after the hn menu.*/
HNHacker.AffectDOMPath("//center[1]/table[1]/tbody[1]/tr[2]", function(node){
	
	var u = HNHacker.MakeElement("td", {
		"id" 	: "HNHacker_UI",
		"style" : "padding-top:0.5em;padding-bottom:0.5em"
	});	
	
	node.appendChild(u);

});

HNHacker.BuildMenu('(//span[@class="pagetop"])[1]', [
	
	// display the localstorage usage and localstorage object in the console
	[" storage ", function(){
		console.log(LocalStorage.usage());
		console.log(LocalStorage.getAll());
	}, [] ],
	
	// DELETE EVERYTHING
	[" clear ", function(){
		window.localStorage.clear();
	}, [] ],
	
	// display following
	[" following ", function(){
		var amFollowing = LocalStorage.get(HNHacker.keys['following']);
		
		for(i =0; i<amFollowing.length; i++){
		
			// add each 'followed' user's profile link to the top menu
			var u = HNHacker.MakeElement("a", {
				"href" : "https://news.ycombinator.com/user?id="+encodeURIComponent(amFollowing[i])
			}, " ["+encodeURIComponent(amFollowing[i])+"] ");	
				
			document.getElementById("HNHacker_UI").appendChild(u);
		}
		
	}, [] ]
]);

/*  iterate each comment, get each username, generate the menu and apply
	the state for that user. */
	
HNHacker.AffectDOMPath('//span[@class="comhead"]', function(item){

	var links = item.getElementsByTagName("a");
	var menu = [];
	
	// count the links and get the user data
	if(links.length > 0){ 
		
		var user = links[0].href;
		var userContext = user.split("=");
		var userName = userContext[1];

		if(arrayContains(this.Users, userName) === false){

			var userState = LocalStorage.get(userName); // this doesn't cache. 
			
			if(typeof userState === 'object'){
				HNHacker.applyUserState(userState, userName, item);
			}
			
			this.Users.push(userName); // keep a queue of username so we don't store multiples

			/* build the menu items for each name.*/
			
			HNHacker.BuildMenu(item, [
			
				["ignore", function(i){ 
					LocalStorage.add(i, HNHacker.keys['ignoring']); 
					HNHacker.applyUserState(HNHacker.keys['ignoring'], i, item);
				}, [userName] ],
				
				["unignore", function(i){ 
					
			/* 	unignoring isn't added to applyUserState because
				there will be nothing to 'apply' after a page
				refresh, we just need to remove the ls element
				and undo the restyling. */
						
					LocalStorage.remove(i, HNHacker.keys['ignoring']); 
					var elem = document.getElementById("ignore_"+i);
					
					elem.parentNode.removeChild(elem);
					
					var target = item.parentNode.parentNode.childNodes[3];
					
					target.style.visibility="visible";
					target.style.position="relative";
				
				}, [userName] ],
				
				["follow", function(i){
					LocalStorage.add(HNHacker.keys['following'], i);
					//HNHacker.applyUserState(HNHacker.keys['following'], i, item);
				}, [userName] ]

			]);
		} 
	}
});