An article to help you learn more about JavaScript arrays

//Define an array through the constructor var array = new Array(); //Empty array with no data

var array name = new Array(length);

var arr = [];
console.log(arr); //Array[0]

var arr1 = new Array(); //Use the constructor to create an empty array var arrr2 = new Array(5); //Use the constructor to create an array of length 5, which has 5 values ​​and all are undefined
var arr3 = new Array(10,20,30,40,50); // The constructor creates an array of length 5, each value has a meaning

//Get the 4th value in the array var arr =new Array(10,20,30,40,100);
console.log(arr[4]); //100
//Change the value of subscript 3 to 1000
arr[3]=1000;
//Get the length of the array using literal value var arr1=[10,20,30,40,50,12];
console.log(arr.length); //6

arr=[10,"哈哈",true,null,undefined,new Object()];

var arr = [];
    // Set the value of an element in an array by index arr[0] = 10;
    arr[1] = 20;
    console.log(arr.length); //2
    // Get the value of the element by index console.log(arr[2]); //undefined

var arr1 = new Array(); //empty array var arr2 = new Array(5); //array of length 5, each array value is undefined
var arr3 = new Array(1, 2, 3, 4, 5); //Array of length 5, each value has meaning var arr4 = []; //Empty array var arr5 = [1, 2, 3]; //Array of length 3 var arr6 = ["red", "blue", 1, true]; //Array of length 4, element data types are different var arr7 = [];
//Declare an empty array and add value to the array arr7[0] = 10;
arr7[1] = 30;

var arr=[10,20,30,40,50,60,70,80,90,100];
// i represents the subscript of the array // The subscript of the last number is equal to the length of the array minus one for(var i=0;i<arr.length;i++){
    console.log(arr[i]);
}

var arr = [10, 20, 30, 40, 100];
// i starts to output the last number, and ends the loop when it reaches 0 for (var i = arr.length - 1; i >= 0; i--) {
    console.log(arr[i]);
}

var arr = [10, 20, 30, 40, 100];
// Used to store the sum after addition var sum = 0;
 for (var i = 0; i < arr.length; i++) {
     sum += arr[i];
 }
 console.log(sum); //200

var arr = [10, 20, 30, 40, 100];
// Used to store the sum after addition var sum = 0;
for (var i = 0; i < arr.length; i++) {
    sum += arr[i];
}
console.log(sum / arr.length); //40

var arr = [10, 20, 30, 40, 100];
// Assume that the first number in the array is the largest and assign it to a variable var max = arr[0];
// Assume that the first number in the array is the smallest and assign it to a variable var min = arr[0];
for (var i = 0; i < arr.length; i++) {
    //Compare the value in the array with max. If it is greater than max, assign that number to max
    if (max < arr[i]) {
        max = arr[i];
    }
    //Compare the value in the array with min. If it is smaller than min, assign that number to min.
    if (min > arr[i]) {
        min = arr[i];
    }
}
console.log(max); //100
console.log(min); //10

var arr = [10, 30, 20, 65, 40, 8, 100];
//Sort from small to large for (var i = 0; i < arr.length; i++) {
    for (var j = 0; j < arr.length - i; j++) {
        if (arr[j] > arr[j + 1]) {
            var temp = arr[j];
            arr[j] = arr[j + 1];
            arr[j + 1] = temp;
        }
    }
}
console.log(arr);
//Sort from large to small for (var i = 0; i < arr.length; i++) {
    for (var j = 0; j < arr.length - i; j++) {
        if (arr[j] < arr[j + 1]) {
            var temp = arr[j];
            arr[j] = arr[j + 1];
            arr[j + 1] = temp;
        }
    }
}
console.log(arr);