function reverse1(input){

  if(typeof input !== 'string'){

      throw new Error('给我字符串啊')

  }

  var output = ''

  for(var i = 0; i< input.length; i++){

    output =  input[i] + output

  }

  return output

}

function reverse2(input){

   if(typeof input !== 'string'){    throw new Error('我只要字符串') }

   return input.split('').reverse().join('')

}

var t1= new Date()

for(var i =0;i<100000;i++){

    reverse1('sakjdlaskjdlaskjdaslkjdaslkjdaslkfjaslkfjaslf;kj')

}

console.log(new Date() - t1)

var t2= new Date()

for(var i =0;i<100000;i++){

    reverse2('sakjdlaskjdlaskjdaslkjdaslkjdaslkfjaslkfjaslf;kj')

}

console.log(new Date() - t2)