general purpose hacker news thing

hackbar.user.js

// ==UserScript==
// @name        HackBar
// @namespace   kennethrapp1@gmail.com
// @description Extras for Hacker News
// @include     https://news.ycombinator.com/*
// @version     1
// @grant       none
// ==/UserScript==

//Returns true if 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 object o 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'
    );
}

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

// remove a value from an array
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;
}

// run a callback on an xpath
function AffectDOMPath(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));
        }
    }
}

// generic html element builder
function MakeElement(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;
}

// generic text control builder
function TextControl(textcontent, callback, args) {
    var control = MakeElement('a', {
        'href': '#',
        'class': 'hn_top'
    }, textcontent);
    control.addEventListener('click', function (event) {
        event.preventDefault();
        callback.apply(this, args);
    }, false);
    return control;
}

// create and return a 'menu' of text controls
function BuildMenu(menu) {
    var menuItem = document.createElement('span');
    for (var i = 0; i < menu.length; i++) {
        menuItem.appendChild(document.createTextNode('['));
        menuItem.appendChild(TextControl.apply(this, menu[i]));
        menuItem.appendChild(document.createTextNode(']'));
    }
    return menuItem;
}

/* controls. Each control is three items - text, function and arguments as an array.*/
var HNMenu = [
    ['watching', function () {alert('test')},[]],
    ['following', function(f){alert(f)}, ['test2']],
    ['ignoring', function(f){  }, []],
];

var UserMenu = [
    ['watch', function(){}, []],
    ['follow', function(){}, []],
    ['ignore', function(){}, []],
]

// xpaths to target 
var HNPath = {
    'UIMain': '//center[1]/table[1]/tbody[1]/tr[2]',
    // blank table row right after the hn menu 
    'MenuTop': '(//span[@class="pagetop"])[1]',
    // top banner/menu
    'Comments': '//span[@class="comhead"]'
};
//.dead
AffectDOMPath("//td | //*[@class='dead']", function(node) {
    node.setAttribute("style","color:#000000;"); 
});

/* create a new table cell in the blank row, style it, create a menu, append the menu. */
AffectDOMPath(HNPath['UIMain'], function (node) {
    node.appendChild(MakeElement('td', {
        'id': 'HNHacker_UI',
        'style': 'padding-top:1em!important;padding-bottom:1em!important'
    }, BuildMenu(HNMenu)));
});

AffectDOMPath(HNPath['Comments'], function (node) {
   node.appendChild(MakeElement('span', {
       'class':'HNuserMenu',
       'style':'padding-left:1em'
   }, BuildMenu(UserMenu))); 
});