URLSearchParams为第一个查询字符串返回null

Question

为什么timeperiod为null

const url = 'http://example.com?timeperiod=lasttwentyeightdays&pagesize=20'
const args =  new URLSearchParams(url);
alert('timeperiod='+args.get('timeperiod') + ' and pagesize='+ args.get('pagesize'));

但是在下面的代码中它可以工作

  const url = 'http://example.com?x=c&timeperiod=lasttwentyeightdays&pagesize=20'
  const args =  new URLSearchParams(url);
  alert('timeperiod='+args.get('timeperiod') + ' and pagesize='+ args.get('pagesize'));