17.数组

1.数组

1.1创建数组

  const arr1 = new Array(); //方法一
  const arr2 = []; //方法二

1.2数组内添加元素

//方法一
const arr2 = [1, 2, 3, 4, 5]; 
//方法二
arr1[0] = 11
arr1[1] = 22
使用数组时，应避免非连续数组，性能不好
arr1[9] = 99

console.log("arr1 = " + arr1); //arr1 = 11,22,,,,,,,,99
console.log("arr2 = " + arr2); //arr2 = 1,2,3,4,5

1.3读取数组元素

 console.log(arr1[0]); //11
 console.log(arr2[0]);//1

 1.4数组长度

 //自定义数组长度
arr1.length = 100
arr2.length = 10
//获取数组长度
console.log(arr1.length); //10
console.log(arr2.length); //5
//数组的数据类型
console.log(typeof arr1); // object
//数组末尾添加元素
arr1[arr1.length] = 123
console.log(arr1[100]);