筛选数组

  <script>
    var arr = [1500, 1200, 2000, 2100, 1800];
    var a = [];
    for (var i = 0; i < arr.length; i++) {
      if (arr[i] < 2000) {
        // a[a.length] = arr[i];
        a.push(arr[i]);
        // 把arr[i]小于2000的数添加给新数组a
      }
    }
    console.log(a);
    console.log(arr);
  script>