My own CMS is currently using J-Query but as one of the goals is to have the whole project to be very small, so I've decided to write my own basic library, I only really need to select elements and modify them using results from my server. (via AJax)

###The Javascript-library v0.01: (Attempt 1) (function(){ a=this.Function; a.prototype.extend=(function(a,b){this[a]=b;return this}); a.prototype.implement=(function(a,b){this.prototype[a]=b;return this}); $=(function(a,b,c){return (b?$(b)[c?c:0]:document).querySelectorAll(a)}) .extend("post",(function(a,b){ c=[]; for(x in a) c[c.length]=[x,a[x]].join("="); d=XMLHttpRequest?new XMLHttpRequest():new ActiveXObject("Microsoft.XMLHTTP"); d.open("POST","./",true); d.setRequestHeader("Content-type","application/x-www-form-urlencoded"); d.onreadystatechange=b; d.send(c.join("&")); return this; })) .extend("each",(function(a,b,c){ for(x in a) if(a.hasOwnProperty(x)) b.call(c, a[x], x, a); return this; })); })();

Okay I know that querySelectorAll can't be relied on, but it is just good for the start of this.

###So what is the point on why I posted this? Simple, this is code-review and I need feedback, Thanks to anyone with the comments.

###The Javascript-library v0.02: (Attempt 2) Okay this is heaps improved (I think) it has reasonable variable names, works better, and most of all is quite buggy. :( Any ideas?

My own CMS is currently using jQuery, but as one of the goals is to have the whole project to be very small, I've decided to write my own basic library. I only really need to select elements and modify them using results from my server (via Ajax).

The JavaScript-library v0.01: (Attempt 1)

(function(){
    a=this.Function;
    a.prototype.extend=(function(a,b){this[a]=b;return this});
    a.prototype.implement=(function(a,b){this.prototype[a]=b;return this});
    $=(function(a,b,c){return (b?$(b)[c?c:0]:document).querySelectorAll(a)})
    .extend("post",(function(a,b){
        c=[];
        for(x in a)
            c[c.length]=[x,a[x]].join("=");
        d=XMLHttpRequest?new XMLHttpRequest():new ActiveXObject("Microsoft.XMLHTTP");
        d.open("POST","./",true);
        d.setRequestHeader("Content-type","application/x-www-form-urlencoded");
        d.onreadystatechange=b;
        d.send(c.join("&"));
        return this;
    }))
    .extend("each",(function(a,b,c){
        for(x in a)
            if(a.hasOwnProperty(x))
                b.call(c, a[x], x, a);
        return this;
    }));
})();

I know that querySelectorAll can't be relied on, but it is just good for the start of this.

The JavaScript-library v0.02: (Attempt 2)

I believe this is much improved. It has reasonable variable names, works better, and most of all is quite buggy.

###The Javascript-library so far: (function(){ a=this.Function; a.prototype.extend=(function(a,b){this[a]=b;return this}); a.prototype.implement=(function(a,b){this.prototype[a]=b;return this}); $=(function(a,b,c){return (b?$(b)[c?c:0]:document).querySelectorAll(a)}) .extend("post",(function(a,b){ c=[]; for(x in a) c[c.length]=[x,a[x]].join("="); d=XMLHttpRequest?new XMLHttpRequest():new ActiveXObject("Microsoft.XMLHTTP"); d.open("POST","./",true); d.setRequestHeader("Content-type","application/x-www-form-urlencoded"); d.onreadystatechange=b; d.send(c.join("&")); return this; })) .extend("each",(function(a,b,c){ for(x in a) if(a.hasOwnProperty(x)) b.call(c, a[x], x, a); return this; })); })();

###Edit: Updated code, Thanks to all, This code is cleaned version from @IvoWetzel;

(function () {
    function $(selector, parentSelector, index) {
        var element = parentSelector ? $(parentSelector)[index || 0] : document;
        return element.querySelectorAll(selector);
    };
    $.extend = function (obj, props) {
        for (var i in props)
            if (props.hasOwnProperty(i))
                obj[i] = props[i];
        return this;
    };
    $.extend($, {
        post: function (data, callback) {
            var params = [];
            for (var i in data)
                if (data.hasOwnProperty(i))
                    params.push([i, data[i]].join('='));
            var req=XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
            req.open('post', '/', true);
            req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
            req.onreadstatechange = callback;
            req.send(params.join('&'));
            return this;
        },
        each: function (obj, func, that) {
            for (var i in obj)
                if (obj.hasOwnProperty(i))
                    func.call(that, obj[i], obj, i);
            return this;
        }
    });
    window.$ = $;
})();

###The Javascript-library v0.01: (Attempt 1) (function(){ a=this.Function; a.prototype.extend=(function(a,b){this[a]=b;return this}); a.prototype.implement=(function(a,b){this.prototype[a]=b;return this}); $=(function(a,b,c){return (b?$(b)[c?c:0]:document).querySelectorAll(a)}) .extend("post",(function(a,b){ c=[]; for(x in a) c[c.length]=[x,a[x]].join("="); d=XMLHttpRequest?new XMLHttpRequest():new ActiveXObject("Microsoft.XMLHTTP"); d.open("POST","./",true); d.setRequestHeader("Content-type","application/x-www-form-urlencoded"); d.onreadystatechange=b; d.send(c.join("&")); return this; })) .extend("each",(function(a,b,c){ for(x in a) if(a.hasOwnProperty(x)) b.call(c, a[x], x, a); return this; })); })();

###The Javascript-library v0.02: (Attempt 2) Okay this is heaps improved (I think) it has reasonable variable names, works better, and most of all is quite buggy. :( Any ideas?

var _    = new function Sample(){};  ////////////////////////////////////////
    _.temp  = {};                    // This Object is intended just for
    _.pages = {};                    // testing, I do the rest in the console
    _.pid   = {};                    // <- Stores the current pageID
    _.el    = {};                    // /PAGE-ID/PAGE-TITLE or #!page=PAGE-ID
    _.fn    = {};                    ////////////////////////////////////////
    _.$    = {};                     // <- Lets leave JQuery alown. :)
(function(){
    this.$ = function(a,b,c){
        if(b&&b.isType("string"))   b = $(b);
        d=b?b[c|0]:document;
        return document.getElementsByClassName.call(d,a);
    };
    var $FP = Function.prototype, $OP = Object.prototype;
    $OP.isType = function (type){
        return typeof this === type;
    }
    $OP.each   = function(fun){ // `fun()` runs 3 times HOW??
        if(this.isType("array")&&this.forEach) return this.forEach(a); // if this is an array and we have a browser with Array().forEach then lets use native code instead.
        if(this.isType("object")||this.isType("array"))
            for(var x in this)
                if(this.hasOwnProperty(x))
                    fun.call(this[x],x,this);
        return this;
    };
    $OP.toString    = function(){
        if(!this.isType("object")&&!this.isType("array")) return this;
        var arr=[];
        this.each(function(a){
            arr[arr.length] = a+"="+this;
        });
        return arr.join("&");
    }
    $FP.multiInput = $FP.MI   = function(){
        var self = this;
        return function(obj){
            if(obj.isType("object")||obj.isType("array"))
                obj.each(function(a,b){
                    self.call(b,a,this);
                });
            else
                self.apply(this,arguments);
            return this;
        };
    };
    $OP.extend = function(key,val){ // I want to add all my functions dynamicly and in bulk.
        (this.prototype||this)[key]=val; // Either myObject.extend("key","val") or my Object.extend({"key":"val"}) work.
        return this;
    }.MI(); // MI/multiInput simply allows objects to be passed instead of making it more sence to use obj.prototype.test=myvalue;
    this.$.extend({
        "post": function(a,b,c,d){
            var e=XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
        e.open("post", a, true);
            e.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
            e.onreadstatechange = function(){
                if(xmlhttp.readyState==4) // Page has fully loaded, now did we get a status code of "200 ok" or an error? Please tell me if "304 Not modified" should be added as run `c` and not `d`
                    (xmlhttp.status==200?c:d).call(xmlhttp.responseText,xmlhttp);
            };
            e.send(b.toString());
            return this;
        },
        "post_json": function(a,b,c){
            return this.post(a,b,function(){
                c.call("return "+$.Function(this)()); // This should run c with this being the object. What works better `()` or `.call()` ?? 
            });
        }
    });
}).call(_); // Lets Leave JQuery alown.

_.$.prototype.each(function(){console.log(this)});

###Edit: Updated code, Thanks to all, This code is cleaned version from @IvoWetzel;

(function () {
    function $(selector, parentSelector, index) {
        var element = parentSelector ? $(parentSelector)[index || 0] : document;
        return element.querySelectorAll(selector);
    };
    $.extend = function (obj, props) {
        for (var i in props)
            if (props.hasOwnProperty(i))
                obj[i] = props[i];
        return this;
    };
    $.extend($, {
        post: function (data, callback) {
            var params = [];
            for (var i in data)
                if (data.hasOwnProperty(i))
                    params.push([i, data[i]].join('='));
            var req=XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
            req.open('post', '/', true);
            req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
            req.onreadstatechange = callback;
            req.send(params.join('&'));
            return this;
        },
        each: function (obj, func, that) {
            for (var i in obj)
                if (obj.hasOwnProperty(i))
                    func.call(that, obj[i], obj, i);
            return this;
        }
    });
    window.$ = $;
})();