什么是数组？

数组是一个特定的变量，它可以保存多个值：

const fruits = ["Apple", "Banana", "Orange"];

---

为什么是数组？

由于 Array 可以存储 n 个值，因此很容易存储和访问数据。

例如：-假设我们必须存储水果的数据，所以我们有两个选择。

选项 1：- 为 n 个fruit创建 n 个变量

let fruit1 = "Apple";
let fruit2 = "Banana";
let fruit3 = "Orange";

选项 2：- 创建一个数组并在其中存储 n 个fruit。

const fruits = ["Apple", "Banana", "Orange"];

---

创建一个数组

复制

COPY

const fruits = ["Apple", "Banana", "Orange"];

使用关键字的另一种方式new

const fruits = new Array("Apple", "Banana", "Orange");

---

访问数组的元素

要访问数组元素，您可以使用它index number，默认情况下index number以0

const fruits = ["Apple", "Banana", "Orange"];
let fruit = fruits[0];

---

改变数组的元素

fruits[0] = "PineApple";

另一种方式

const fruits = ["Apple", "Banana", "Orange"];
fruits[0] = "PineApple";

---

访问数组的所有元素

复制

COPY

const fruits = ["Apple", "Banana", "Orange"];
document.getElementById("demo").innerHTML = fruits;

---

数组方法

.length（）

const fruits = [
     "Apple", 
     "Banana", 
     "Orange",
     "Pineapple"
  ];
 
console.log(fruits.length); 

// output:-
// 4

.pop（）

该pop方法用于移除数组的最后一个元素

const fruits = [
    "Apple", 
    "Banana", 
    "Orange",
    "Pineapple"
];

let removefruit = fruits.pop()


console.log(`${removefruit}  removed from the array`);
console.log(fruits);

// output

// "Pineapple  removed from the array"
// [object Array] (3)
// ["Apple","Banana","Orange"]

.push（）

push()方法用于在数组末尾添加元素

const fruits = [
    "Apple", 
    "Banana", 
    "Orange",
    "Pineapple"
];

console.log(fruits);

fruits.push("Watermelon")

console.log(fruits);

// output

// ["Apple","Banana","Orange","Pineapple"]
// ["Apple","Banana","Orange","Pineapple","Watermelon"]

.concat

.concat用于合并两个数组的值

const fruits = [
    "Apple", 
    "Banana", 
    "Orange",
    "Pineapple"
];
const vegetables = [
    "Carrots",
    "Potatoes",
    "Chilli"
];

let vegetablesAndFruits = vegetables.concat(fruits)

console.table(vegetablesAndFruits);

// output:-
// ["Carrots","Potatoes","Chilli","Apple","Banana","Orange","Pineapple"]

.indexOf（）

.indexOf用于查找index number给定数组元素的

const fruits = [
    "Apple", 
    "Banana", 
    "Orange",
    "Pineapple"
];

console.log(fruits.indexOf("Orange"));

// output:-
// 2

.lastIndexOf()

lastIndexOf()用于查找项目最后一次重复的时间

let travelHistory = ["Rome", "India", "Russia", "Nepal", "Dubai", "India"];

console.log(travelHistory.lastIndexOf("Rome")); // 0
console.log(travelHistory.lastIndexOf("India")); // 5
console.log(travelHistory.lastIndexOf("Russia")); // 2
console.log(travelHistory.lastIndexOf("canada")); // -1

.join（）

const fruits = ["apple", "banana", "orange"]

let fruitsStr = fruits.join(" & ")
console.log(fruitsStr);

// Output:-
// "apple & banana & orange"

.reverse（）

.reverse()方法用于以相反的顺序定位数组的元素

const fruits = ["apple", "banana", "orange"]

let fruit = fruits.reverse()
console.log(fruit);

// output:-
// ["orange","banana","apple"]

.sort（）

const fruits = ["banana","pineapple", "orange", "apple"]


fruits.sort()
console.log(fruits);

// output:-
// ["apple","banana","orange","pineapple"]

.toString()

const fruits = ["banana","pineapple", "orange", "apple"]


console.log(fruits.toString());


// output:-
// "banana,pineapple,orange,apple"

.copyWithin()

const fruits = ["banana","pineapple", "orange", "apple"]


// (target,start,end)
// end option
fruits.copyWithin(0, 2, 3)
console.log(fruits);

// output:-
// ["orange","pineapple","orange","apple"]


Resources

文章来源：https://themohitgupta.hashnode.dev/array-in-javascript