lazyAPI = {

    indexOf : function(func) {
        this.funcs.push(func);
        return this.funcs.length - 1;
    },

    addFunc : function(strFunc) {
        this.strHandler += strFunc;
    },

    forEach : function(fn) {
        var i = this.indexOf(fn);
        this.addFunc('fns['+i+'](el,i);');
        return this;
    },

    filter : function(fn) {
        var i = this.indexOf(fn);
        this.addFunc('if(!fns['+i+'](el,i)) return;');
        return this;
    },

    map : function(fn) {
        var i = this.indexOf(fn);
        this.addFunc('el = fns['+i+'](el,i);');
        return this;
    },

    get array() {
        var
            arr = this.arr,
            fns = this.funcs,
            out = [], i = 0,
            lenA = arr.length,
            str = this.strHandler + 'out.push(el);',
            handler = new Function('el,i,fns,out', str);

    /*
        var lastA = lenA - 1;
        for (; (i+=2) < lastA;) {
            handler(arr[i], i, fns, out);
            handler(arr[i+1], i+1, fns, out);
        }
        if((lastA+1) % 2 === 1) handler(arr[lastA], lastA, fns, out);
    */

        for(; ++i < lenA;) handler(arr[i], i, fns, out);
        return out;
    }
};

getterLazy = function() {
    var lazy = Object.create(lazyAPI);
    lazy.arr = this;
    lazy.funcs = [];
    lazy.strHandler = '';
    return lazy;
};

if(Object.defineProperty) {
    Object.defineProperty(Array.prototype, 'lazy',
        { get : getterLazy, enumerable : true, configurable : true });

} else if({}.__defineGetter__) {
    Lazy.prototype.__defineGetter__('array', getterArray);
}

/* TESTING */
function fill(size) {
    var arr = [];
    for(var i = 0; i < size ; ++i) arr[i] = i;
    return arr;
}

var arrays = {};
function check(size, chain) {
    var arr = arrays[size] || (arrays[size] = fill(size));
    var sizeExp = size.toExponential();

    console.time('Default(' + sizeExp + ')');
    for(var i = 0; i < 100; ++i)
        chain(arr);
    console.timeEnd('Default(' + sizeExp + ')');

    console.time('Lazy(' + sizeExp + ')');
    for(var i = 0; i < 100; ++i)
        chain(arr.lazy).array;
    console.timeEnd('Lazy(' + sizeExp + ')');

}

chainOf2 = function (arr) {
    return arr
        .map(function(x){ return x-50 })
        .filter(function(x){ return x > 0});
};

chainOf4 = function (arr) {
    return arr
        .map(function(x){ return x-50 })
        .filter(function(x){ return x > 0})
        .map(function(x){ return x * 5 })
        .filter(function(x){ return x % 2});
};

chainOf6 = function (arr) {
    return arr
        .map(function(x){ return x-50 })
        .filter(function(x){ return x > 0})
        .map(function(x){ return x * 5 })
        .filter(function(x){ return x % 2})
        .map(function(x){ return x - 50 })
        .forEach(function(x){ x + 100 });
};

check(1e3, chainOf6);