factorial_array_5digit.js

(function(){

    function multiplyStrings(a,b){
        var result = [];

        for(var i=0; i < b.length; i++) {
               result = addToStringumbers(result,multiplyWithOneDigit(a,b[i]));
        }
        return result;
    }

    function multiplyWithOneDigit(a,b){
        var result      = new Array(a.length);
        var carry       = 0;
        for(var i=0; i < a.length; i++) {
	   var op = a[i]*b+carry;
           carry = (op/100000)|0;
	   result[i] = (op%100000); 
        }
	if( carry ) result.push(carry);
        return result;
    }


    function addToStringumbers(a,b){
        if(a.length == 0)
            return b;

        var carry = 0;
        var result = new Array(b.length);

        for(var i=0; i < a.length; i++){
           var op = a[i]+b[i]+carry;
   	   carry = (op/100000)|0;
           result[i] = ( op%100000 );
        }
        for( ; i < b.length; i++){
           var op = b[i]+carry;
   	   carry = (op/100000)|0;
           result[i] = ( op%100000 );
        }
        if(carry) result.push( carry );

        return result;
    }

    function intToArray(i) {
	//if( i < 100000 )
		return [i];
	//else
	//	return [i %100000, i / 100000]
    }

    function factorial(x){
        var result = [1];
	var thisNum = [0];
        for(var i=2; i<=x; i++){
            thisNum[0] = i;
            //result = addToStringumbers(result,multiplyWithOneDigit(result,i));
	    result = multiplyStrings(result,thisNum);// intToArray(i));
        }
	
        var tmp = result.reverse();
	var tmp2 = tmp.map( (n,i)=>{ 
            var s = n.toString(10);
            if( i ) for( var n = s.length; n < 5; n++ ) s = "0" + s; 
            return s } );
	return tmp2.join("");
	
    }

var now = Date.now();
    console.log(factorial(process.argv[2]));
console.log( "del:", Date.now() - now );

}());