Isso

isso.js

var isso = (function(root){
    var value = undefined;
    
    function isso(v){
        return (v)? new inner(v): ex;
    }
    
    function inner(v){
        this.value = v;
        return this;
    }

    // Undefined?    
    inner.prototype.undef = function undef(){
        return (this.value === null || this.value === undefined);
    }
    
    // Defined?
    inner.prototype.def = function def(){
        return !this.undef();
    }
    
    inner.prototype.empty = function(){
        return (this.def() || this.value === {} || this.value === "" || this.value === []);
    }
    
    inner.prototype.falsy = function falsy(){
        return (this.undef() || this.empty() || this.value === 0 || this.value === false);
    };
    
    inner.prototype.truthy = function truthy(){
        return !this.falsy();
    };

    inner.prototype.type = function type(){
        return Object.prototype.toString.call(this.value).slice(8, -1).toLowerCase();
    };
    
    var ex = {
        extend: function(name, fn) {
            inner.prototype[name] = fn;
        }
    };
    
    return isso;
    
})(this);