1. 创建数组的两种方式
方式一：

var numbers = [10,20,30];

console.log(numbers);

如图所示：

方式二：

numbers = new Array(100,200,300);

console.log(numbers);

如图所示：

2. 二维数组 把所有的数字取出来,保存到 bigNumbers 数组中
numbers = new Array(100,200,300);

var arr = [numbers,[1000,2000,3000,4000]];

var bigNumbers = [];

console.log(arr);

for (var i = 0; i < arr.length; i++) {

console.log(arr[i]);

for (var n = 0; n < arr[i].length; n++) {

console.log(arr[i][n]);

bigNumbers.push(arr[i][n]);

}

}

console.log(bigNumbers);

如图所示：

3.var l = numbers.push();    特点:修改原数组,末尾添加
numbers = [];

var l = numbers.push(10,11,12,13);

console.log(numbers,l);

如图所示：

4.var l =  numbers.unshift(开头1,2,3...n末尾);    特点:修改元素组,开头添加
var l = numbers.unshift(1,2,3);

console.log(numbers,l);

如图所示：

5. var l = numbers.pop();  特点:修改原数组,末尾删除一个
var l = numbers.pop();

console.log(numbers,l);

如图所示：

6. var l = numbers.shift();  特点:修改原数组,开头删除一个
var l = numbers.shift();

console.log(numbers,l);

如图所示：

7.array.splice(index,howmany,item1,.....,itemX)
splice() 方法用于添加或删除数组中的元素。
注意：这种方法会改变原始数组。
var sites = ["taobao","daxue","lanou","jingdong"];

// 删除两个,可以添加一个或多个,也可以不添加

var deleteSites = sites.splice(1,2,"baidu","google");

console.log(sites,deleteSites);

如图所示：

// 只添加,不删除

var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.splice(2,0,"Lemon","Kiwi");

console.log(fruits);

如图所示：

8.该范围产生的新数组 = array.slice(start,end)
[start,end) 包含开始位置,不包含结束位置
注意: slice() 方法不会改变原始数组

var fruits = ["Banana", "Orange", "Apple", "Mango"];

var arr = fruits.slice(1,3); // 截取中间两个

console.log(fruits,arr);// 原数组保持不变

如图所示：

 
9. indexOf() : 返回元素所在的位置
array.indexOf(item,start)
参数2：规定在数组中开始检索的位置,找到后立马结束

var fruits=["Banana","Orange","Apple","Mango","Banana","Orange","Apple"];

var a = fruits.indexOf("Apple",4);

console.log(fruits,a);

如图所示：

10.isArray() 方法用于判断一个对象是否为数组(ie9+支持)
如果对象是数组返回 true,否则返回false
区分对象和数组的小技巧:
技巧:找有个数组特有的属性或者方法,判断变量是否具有,对的话返回undefined

var a = {} , b = [];

console.log(Array.isArray(a),Array.isArray(b));

// 对象返回undefined 数组返回长度

console.log(a.length,b.length);

console.log(a.pop,b.pop)

if(a.length == undefined) {

console.log("a不是一个数组")

} else {

console.log("a是一个数组")

}

如图所示：

11.concat() 方法用于连接两个或多个数组。
array1.concat(array2,array3,...,arrayX)
该参数可以是具体的值，也可以是数组对象。可以是任意多个。
该方法不会改变现有的数组，而仅仅会返回被连接数组的一个副本。

var arr1 = [1,2];

var arr2 = [10,20];

var arr3 = [100,200];

var arr = arr1.concat(arr2,arr3);

console.log(arr1,arr);

如图所示：

// 使用技巧: 复制一个数组

var copyArr1 = arr1.concat();

// 地址的拷贝赋值

var nums1 = arr1;

console.log(arr1,copyArr1,nums1);

// 原数组更新,副本不会变化,但是直接赋值的nums1会变化

arr1.push(3);

console.log(arr1,copyArr1,nums1);

如图所示：

12.toString() 方法可以数组转换为字符串,并返回结果
var arr1 = [1,2,3];

var str = arr1.toString();

var str1 = false.toString();

console.log(str,typeof str); // 1,2,3 string

console.log(str1,typeof str1);

如图所示：

13.join() 数组->字符串
1. 通过指定的分隔符进行分割的。假如不穿参数,会以逗号分割

var arr1 = [1,2,3];

var str = arr1.join("-");

console.log(str,typeof str); // 1-2-3 string

如图所示：

       2. 不需要分隔符: 给空的字符串

var arr1 = [1,2,3];

var str = arr1.join("");

console.log(str, typeof str); // 123 string

如图所示：

14. reverse() 原数组和返回值都是反转后的数组
var arr1 = [1,2,3];

var revArr = arr1.reverse();

console.log(revArr,arr1);

如图所示：

15. split() 字符串->数组
var arr = "1-2-3-4".split("-"); // ["1", "2", "3", "4"]

// 不传参数,整个字符串变成数组的一个元素

var arr = "1-2-3-4".split(); // ["1-2-3-4"]

// 空字符串,把每一个字符变成数组中的一个元素

var arr = "1-2-3-4".split(""); // ["1", "-", "2", "-", "3", "-", "4"]

console.log(arr);

如图所示：

 
16.题目: 把字符串 var name = "cuiAoDi", 反向输出
var name = "daXueSheng";

// 1.变成数组

var nameArr = name.split("");

console.log(nameArr);

// 2.翻转

nameArr.reverse();

console.log(nameArr);

// 3.变回在字符串

name = nameArr.join("");

console.log(name); // gnehSeuXad

如图所示：

var value = "123456".split("").reverse().join("");

console.log(value); // 654321

如图所示：

 
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版权声明：本文为CSDN博主「会过敏的企鹅」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/qq_43623306/article/details/90729226

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