the C# 'yield' implementation in javascript

yield.js

// the C# 'yield' implementation in javascript
!function(){
    window.yield = function(func){
        this._bodyFunc=null;
    };
    
    var p = yield.prototype;
    
    p.body = function(func){
        this._bodyFunc = func;
    };
    
    p.calc = function(func){
        this._calcFunc = func;
    };
    
    p.enum = function(){
        try{
            this._calcFunc.apply(this, arguments);
        }
        catch(ex){
            if (ex.type != 'yield.break'){
                throw ex;
            }
        }
    };
    
    p.ret = function(value){
        this._bodyFunc.call(this, value);
    };
    
    p.brk = function(){
        throw {type: 'yield.break'};
    };
}();


!function(undef){
    "use strict";
    var noConflict = null;
    
    var chn = function(obj){
        return new wrapperCtor(obj);
    };
    
    chn.noConflict = function(){
        if (noConflict){
            window._0 = noConflict;
        }
        
        return chn;
    };
    
    var wrappers = {
        func: function(context, propName){
            return function(){
                var ret = context[propName].apply(context, arguments);
                    
                // if no return value, return myself
                if (ret === undef){
                    return this;
                }
                return ret;
            };
        },
        prop: function(context, propName){
            return function(value){
                if (value === undef){
                    return context[propName];
                }
                else{
                    context[propName] = value;
                    return this;
                }
            };
        }
    };
    
    /**
     * Wrapper Private Methods
     */
    var wrapperPrvt = {
        /**
         * @function init
         * Copy over all members from obj and create corresponding chain-style
         * wrapping function.
         */
        init: function(obj, enableYield){
            this._0_target = obj;
            var type;
            for(var name in obj){
                type = Object.prototype.toString.call(obj[name]).toUpperCase();
                if (type.indexOf('FUNCTION') > 0){
                    this[name] = wrappers.func(obj, name);
                }
                else{
                    this[name] = wrappers.prop(obj, name);
                }
            }
        }
    };
    
    var wrapperCtor = function(obj, enableYield){
        wrapperPrvt.init.call(this, obj, enableYield);
    };
    
    wrapperCtor.prototype = {
        _0_rebuild: function(){
            wrapperPrvt.init.call(this, this._0_target);
            return this;
        }
    };
    
    
    // shorthand method
    if (window._0 != null){
        noConflict = window._0;
    }
    
    window._0 = chn;
    window.chainit = chn;
}();


// Example

chainit(new yield).body(function(i){if (i > 16) {this.brk()} console.log(i)}).calc(function(num, exp){var counter=0; result=1; while(counter++<exp){result*=num; this.ret(result)}}).enum(2, 8)