10进制转2进制的尾递归版本

[zwhu]

这是一篇水文，老板给面试同学出的笔试题，顺手练一下

function toBinary(n) {
  function toBinaryIter(n, s) {
     if(n === 0) {
       return s || '0'
     }

     var a = n / 2
     , b = n % 2

     return toBinaryIter(a|0, b+s)
  }

  return toBinaryIter(n, '')
}

toBinary(0) === (0).toString(2)

toBinary(1) === (1).toString(2)

toBinary(3) === (3).toString(2)

toBinary(10) === (10).toString(2)

toBinary(101) === (101).toString(2)