Learning Js Basic Day 6 Objects and Built-in Objects Math,Date

    What is the object?
    Something visible, tangible, specific

    Object Finding: Describing Object Finding

    Object: What are the characteristics of the object: characteristics and behavior

    Summarize what is the object
    Object: Something with characteristics and behavior, specific characteristics
    Object: Something with attributes and methods, specific characteristics

    No Objects Create Objects
    The Set of Unordered Attributes

There are four things you do when you customize the creation of new objects
    1. Create (apply for a free) space in memory to store new objects
    2. Set this as the current object
    3. Setting the value of the object's properties and methods
    4. Return this object.

Ordinary function, lowercase beginning: mainly used to call
    function person() {
Custom constructor, capitalized beginning: used primarily to create objects
    function Person () {

Object. Attribute or Method - ------------- Create Object Attribute or Method. If this Attribute exists, it will be assigned from a new value. If not, it will be created.

Object ["attribute"] - ------------------------------------------------------------------------------------------------------------------------------------------------

javascript is a scripting language
            It's an interpretative language.
            Is an object-based language
            It is a weak language.
            It's a dynamic language: 1. Code only knows what is stored when it's in this position. If it's an object, there are attributes and methods of the object. If it's a variable, there are functions of the variable. 2. Objects have nothing. As long as you click, you can add attributes and methods to the object.
Object, Attribute, Object, Method () ------- Object ["Attribute"], Object ["Method"] ()
A Set of Unordered Attributes--Objects
How to create objects
 1. Creating objects through system functions
            var obj = new Object();
            // Object's attribute object. Name = value;
            obj.name = Xiaosu;
            obj.age = 17;
            // Add method object. Name = function;
            obj.eat = function () {
                console.log("I like the Year of the Ox");
Create objects by literal quantities
        var o ={} ;   //Empty objects, like constructs
         obj.name = "Xiao Bai";
        obj.age = 10;
        obj.sayHi = function () {
            console.log("I am:"+this.name);
//Disadvantage: Outside the object
//For a disposable object outside the object, the change value can only be changed inside the object, but cannot be passed on.
    var o = {
            name : "Zhang San",
             sex : "true",
            study : function () {
                return "like to study";
    console.log("One is called"+ o.name+"Gender is"+ o.sex+ o.study());
Create Objects by Customization
     function obj (name,age) {
        this.name = name;
        this.age = age;
        this.study = function () {
            console.log("like to study");
        this.study ();
    var p1 = new obj ("Zhang San",3);
json The format should be enclosed in double quotation marks regardless of the value or key. It is out of order and can not be used. for loop
k What is stored is json Name of object attribute(Character string),key Not that attributes are unavailable json["key"]But json[key]
    var json = {
        "name" : "xiao",
        "age" : "11",
        "sex" : "nan"
    json.height = 180;
    for (var k in json) {
        console.log(json.k);  //Create attributes, three undefined; object name. Attribute creation, if any, is reproduced, if not purely create attributes
//        console.log(json[k]);
//    }



Math object

Instance objects: Objects instantiated by constructors (via new)

Static object: No need to create, directly out is an object, the method is called through the static object (Math)

Example method: new

Static method: Math.name, Array.isArray pointed out directly by the object

var random=Math.random();
  floor=Math.floor(14.2);//Downward Forensics
  round=Math.round(15.22);//round around
  abs=Math.abs(-22);//Absolute value
  ceil=Math.ceil(random);//Upward Forensics
  random=parseInt(random);//Pay attention to random reception
var power= Math.pow(2,4);//pow is the y power of x
  var sqrt=Math.sqrt(9);
  console.log(sqrt);   //square root

Date object

    var dt = new Date ();
    console.log(dt);          // Current Standard Time: Thu Sep 06 2018 00:07:16 GMT+0800 (China Standard Time)

    var dt = new Date ("2018-9-5"); //Pass the string type directly, showing the Date type (time type)
    console.log(dt);                 //Wed Sep 05 2018 00:00 GMT+0800 (China Standard Time)

    var dt = new Date (2018,9,4);
    console.log(dt);                //Thu Oct 04 2018 00:00 GMT + 0800 (China Standard Time)

    var dt = new Date (2018/9/4);
    console.log(dt);               //Thu Sep 01 1970 08:00 GMT+0800 (China Standard Time)

    var now = new Date ()
    console.log(now.valueOf());   //Get the number of milliseconds from January 1, 1970

    var dt =Date.now()
    console.log(dt)                    //Get the number of milliseconds from January 1, 1970

    var dt = new Date ();
    console.log(dt.getTime ());
    console.log(dt.getSeconds());  //Return to 0-59
    console.log(dt.getMinutes());  //Return to 0-59
    console.log(dt.getHours());  //Return to 0-23
    console.log(dt.getDay());  //Return to Wednesday
    console.log(dt.getDate());  //Return to the day of the month
    console.log(dt.getMonth());  //Back to this month, starting at 0.
    console.log(dt.getFullYear());  //Return to the year of four

 //Formatting date: September 6, 2018, 8:27:40:
    var dt = new Date ();
    var year =dt.getFullYear();
    var month = dt. getMonth()+1;   //Month begins at 0 and must be added 1
    var day = dt.getDate();
    var hour = dt.getHours();
    var minute = dt.getMinutes();
    var second = dt.getSeconds();

Keywords: Attribute JSON Javascript

Added by dunnsearch on Sun, 19 May 2019 03:00:41 +0300