数组

数组(Array)

数组的创建

1.var arr = new Array();
2.var arr =[];(常用)

数组元素的类型

数组中可以存放任意类型的数据，例如字符串，数字，布尔值
var arr  =['小白',12,true,22.2];

获取数组元素

//声明数组
  var arr = ["tom", "jim", "lass", "tia"];
  //获取数组元素
  console.log(arr[0]);
  console.log(arr[1]);
  console.log(arr[2]);
  //遍历数组
  for (var i = 0; i < arr.length; i++) {
    console.log(arr[i]);
  }
  //求数组[2,6,1,7,4]里面所有元素的和以及平均值
  var arrn = [2, 6, 1, 7, 4];
  var sum = 0;
  var avg = 0;
  for (var i = 0; i < arrn.length; i++) {
    sum += arrn[i];
  }
  avg = sum / arrn.length;
  console.log(sum, avg);
  //求数组[2,6,2,77,52,25,7]中的最大值
  var arr = [2, 6, 2, 77, 52, 25, 7];
  var max = arr[0];
  for (var i = 0; i < arr.length; i++) {
    if (max < arr[i]) {
      max = arr[i];
    }
  }
  console.log(max);
  //将['red','green','blue','pink']转换为字符串，并且用|或其他符号分割，输出red|green|blue|pink
  var arr = ["red", "green", "blue", "pink"];
  var str = "";
  var sep = "|";
  for (var i = 0; i < arr.length; i++) {
    str += arr[i] + sep;
  }
  console.log(str);
  //新增数组元素，修改length长度
  var arr = ["red", "green", "blue", "pink"];
  console.log(arr);
  arr.length = 10;
  console.log(arr);
  //新增数组元素，修改索引号 *不要给数组名直接赋值，否则数组会被重新赋值
  var arr = ["red", "green", "blue", "pink"];
  console.log(arr);
  arr[4] = "sss"; //新增数组元素
  arr[0] = "aaa"; //修改数组元素
  console.log(arr);
  arr = "a";
  console.log(arr);
  //新建一个空数组，向空数组存放10个整数1-10
  var arr = [];
  for (var i = 1; i <= 10; i++) {
    arr[i - 1] = i;
  }
  console.log(arr);
  //将数组[2,0,6,1,77,0,52,0,25,7]中大于等于10的元素选出来，放入新数组
  var arr = [2, 0, 6, 1, 77, 0, 52, 0, 25, 7];
  var arr1 = [];
  var j = 0;
  for (var i = 0; i < arr.length; i++) {
    if (arr[i] >= 10) {
      arr1[j] = arr[i];
      j++;
    }
  }
  console.log(arr1);

  //将数组[2,0,6,1,77,0,52,0,25,7]中的0去掉，形成以个不包含0的数组
  var arr = [2, 0, 6, 1, 77, 0, 52, 0, 25, 7];
  var arr1 = [];
  for (var i = 0; i < arr.length; i++) {
    if (arr[i] != 0) {
      arr1[arr1.length] = arr[i];
    }
  }
  console.log(arr1);
  //反转数组
  var arr = ["red", "green", "blue", "pink"];
  var arr1 = [];
  for (var i = 0; i < arr.length; i++) {
    arr1[i] = arr[arr.length - i - 1];
  }
  console.log(arr1);
  //冒泡排序
  var arr = [2, 0, 6, 1, 77, 0, 52, 0, 25, 7];
  for (var i = 0; i < arr.length - 1; i++) {
    for (var j = 0; j < arr.length - 1 - i; j++) {
      if (arr[j] > arr[j + 1]) {
        var temp = arr[j];
        arr[j] = arr[j + 1];
        arr[j + 1] = temp;
      }
      // console.log(arr);
    }
  }
  console.log(arr);