recude-map.js

(function (/* 01. reduce (v, fn, b) */) {
    
    var reduce = function (v, fn, b) {
        return reduceAux (v, fn, b, 0, b);
        
    };
    
    var reduceAux = function (v, fn, b, p, ac){
    	return p > v.length - 1 ?
    		ac :
    		reduceAux(v, fn, b, p+1, fn(ac, v[p], p, v ));
    };
    

		var map = function (v, fn) {
      return reduce (v, function (ac, e, i, v) {
          return ac.concat (fn (e, i, v));
      }, []);
    };
    
/*    //2
    var map = function map (v, fn) {
    	return reduce(v, mapAux(v, fn), []);
    }
    
    var mapAux = function(v, fn ){
    	return function(ac, e, p, v ){
    		return ac.concat(fn (e, p, v));
    	}
    };*/
    
    //3 Doesn't work
/*    var map = function map (v, fn) {
  	 	return reduce(v, mapAux.bind(this), []);
    }
    
    var mapAux = function(ac, e, p, v ){
  		return ac.concat(this.fun(e, p, v));
    };*/
    
    var add = function (x, y) { return x + y; };
    var mul = function (x, y) { return x * y; };
    var odd = function (x, y) { return !y;  };
    var cnt = function (x, y) { return y+1; };
    console.log (
        reduce ([1,2,3,4,5], add, 0),       // 15
        reduce ([1,2,3,4,5], mul, 1),       // 120
        reduce ([1,2,3,4,5], odd, true),    // false
        reduce ([1,2,3,4,5], cnt, 0)        // 6
    );
    console.log (
        map ([1,2,3,4,5], function (x){ return -x; }),  // [ -1, -2, -3, -4, -5 ]
        map ([1,2,3,4,5], function (x){ return x*x; })  // [ 1, 4, 9, 16, 25 ]
    );
    
})();