CSS Conf 投资

lucky.js

var range = function(num) {
  return Array(num).fill(1).reduce(function(ret, item, i) {
    return ret.concat(i + 1);
  }, []);
};

var select = function(num) {
  var ID = '___list';
  var list = window[ID] || localStorage.getItem(ID);
  
  if(typeof list === 'string') list = JSON.parse(list);
  
  if(!list) {
    num = +num;
    if(isNaN(num)) throw '人数只能是数字';
    list = range(num);
  }
  
  window.addEventListener('beforeonload', function() {
    if(list.slice) localStorage.setItem(ID, JSON.stringify(list));
  });
  
  var random = Math.floor(Math.random() * list.length);
  var lucky = list[random];
  
  list.splice(random, 1);
  window[ID] = list;
  
  return lucky;
};


select(100);