var arr2 = [1, 2, 3]
 arr2.push(4, 5, 6)
 console.log(arr2) //[1,2,3,4,5,6]

var arr3 = [1, 2, 3]
arr3.unshift(4, 5, 6)
  console.log(arr3) //[4, 5, 6, 1, 2, 3]

  var arr4 = [1, 2, 3]
  arr4.splice(1, 1, 888, 999)
  console.log(arr4) //索引1开始，删除1个元素，然后增加888，999

  var arr5 = [1, 2, 3]
  arr5.splice(1, 0, 888, 999)
  console.log(arr5) //索引1开始，删除0个元素，然后在索引1前增加888，999

 var arr6 = [1, 2, 3]
  arr6.splice(1, 1)
  console.log(arr6) //索引1开始，删除1个元素

var arr7 = [1, 2, 3]
  arr7.pop()
  console.log(arr7)

var arr8 = [1, 2, 3]
  arr8.shift()
  console.log(arr8)

 var arr9 = [4, 5, 6, 's']
  console.log(arr9.indexOf('s')) //3

var arr10 = [4, 5, 6, 's']
  console.log(arr10.join("-")) //4-5-6-s

 - var arr11 = [1, 2, 3]
  var arr11 = arr11.concat(7, 8, 9)
  console.log(arr11) //7，8，9合并到arr11
  var arr12 = [4, 5, 6]
  var arr13 = [7, 8, 9]
  console.log(arr12.concat(arr13)) //arr13合并到arr12

 var arr14 = [1, 2, 3]
  console.log(arr14.reverse()) //[3, 2, 1]

var arr15 = [8, 6, 2, 4, 3, 1, 7, 5]
  console.log(arr15.sort()) //[1, 2, 3, 4, 5, 6, 7, 8]

var arr = [1, 2, 3, 81, 95, 3];
  a = arr.sort(function(a, b) {
   return (a - b);
  });
  console.log(a);
  ary.sort(function(a, b) {
   return (a - b);
  })