【JS】数値に関連する様々な計算処理メモ ref: http://qiita.com/kingpanda/items/8d95bc3b32057031a3da

file0.js

/* 数値の桁数を表示 */

var Count = function(e){
  var num = e,
      digit = 0;
  if(num == 0){
    return 1;
  }else{
    while(num !== 0){
      num = (num/10) << 0;
      digit++;
    }
    num = digit;
    return num;
  }
}

console.log(Count(293892));

file1.txt

6

file2.js

/* 整数を逆順に並べ替え */

var Reverse = function(e){
  var num = e,
      digit = 0;
  if(num < 0){
    return -1;
  }else if(num == 0){
    return 1;
  }else{
    while(num > 0){
      digit = digit * 10 + num % 10;
      num = (num/10) << 0;
    }
    num = digit;
    return num;
  }
}

console.log(Reverse(9450356));

file3.txt

6530549

file4.js

/* 整数を逆順に並べ替え */

var Factorial = function(e){
    var num = e;
    if(num < 0){
        return -1;
    }else if(num == 0){
        return 1;
    }else{
        return (num * Factorial(num - 1));
    }
}

console.log(Factorial(10));

file5.txt

3628800