javascript实现随机读取数组的方法

function write_quote() {
  var quotes = [
    'no animals were harmed while making this page',
    'made in ulm',
    'this page was handmade',
    'Get <a href="http://www.mozilla.org/products/firefox/">FireFox</a> :-)'
  ];
  var r = Math.round(Math.random() * (quotes.length-1));
  // write the quote
  document.write(quotes[r]);
  // or replace an HTML element:
  // document.getElementById("quote").innerHTML = quotes[r];
}