Programming thought: integrate some experience of doing things in life into the program
Process oriented: do everything by yourself, focusing on the process.
Object oriented: find objects according to requirements, do everything with objects, and focus on results
Object oriented features: encapsulation, inheritance, polymorphism (abstraction)
JavaScript is not an object-oriented language, but an object-oriented language. It can be regarded as an object-oriented idea
Everything is object ---> js advanced
What is an object? Something that can be seen or touched
Characteristics of the analysis object:
features ---> attribute
behavior ---> method
There are three ways to create objects:
-- Call the system constructor to create the object
var obj = new Object();
- Add / set attribute: object. Attribute name = Value;
- Add / set method: object. Method name = Anonymous function;
Data storage form: key value pair
var ojb = new Object()
ojb.name = 'Xiao Ming';
ojb.age = 19;
ojb.jn = function(){
console.log("I am" + ojb.name + "I" + ojb.age + "year")
}
console.log(ojb);
ojb.jn()
-- Creating objects with custom constructors
Define a constructor yourself
The difference between a function and a constructor: the constructor's name is capitalized
function Dx(name, age){
this.name = name,
this.age = age,
this.jn = function (){
console.log("I am" + this.name + "I" + this.age + "year")
}
}
var cl = new Dx("Xiao Ming",19);
console.log(cl)
cl.jn();-- Create objects literally (two methods)
Method 1:
var cl = {};
cl.name = "Xiao Ming";
cl.age = 19;
cl.jn = function(){
console.log("I am" + this.name + "I" + this.age + "year")
}
console.log(cl);
cl.jn();Method 2:
var cl = {
name : "Xiao Ming",
age : "19",
jn : function(){
console.log("I am" + this.name + "I" + this.age + "year")
}
}
console.log(cl)
cl.jn();The results of the above codes are:
Create objects in factory mode
There is a way to combine the above methods to create objects in batches in a factory
function dog(color, breed, age, jn){
var obj = new Object();
obj.color = color,
obj.breed = breed,
obj.age = age,
obj.jn = function(){
console.log(jn);
};
return obj;
}
mao1 = new mao("gules", "Siberian Husky", 2 , "Catch fish");
mao2 = new mao("yellow", "Golden hair", 5, "sleep");
console.log(mao1);
console.log(mao2);
mao1.jn();
mao2.jn()Three objects for JavaScript learning:
1. Built in objects -- objects of JavaScript system: Math, Date, String, Array, Object
2. Custom object --- the object created by the constructor defined by yourself
3. Browser object
Instance object: an object created by constructor
Static object: it does not need to be created. It is an object directly. Methods / attributes can be called directly through the method name
Math objects: static objects
- Math.PI Pi Pi
- Math.floor (value) Round down
- Math.ceil (value) Round up
- Math.abs (value) absolute value
- Math.round (value) Round off, positive numbers round off, negative numbers ignore symbols first and round off
- Math.max (many numbers) Take the maximum value
- Math.min (many numbers) Take the minimum value
- Math.pow(m, n) The value of m to the nth power
- Math.sqrt(16) Open square root
- Math.random() Take random number, interval 0-1
Date object
// Create specified time
var dt = new Date("2011-11-30 20:42:12");
console.log(dt);
// Get the current time and create an instance object
var dt2 = new Date();
console.log(dt2);
// Gets the number of milliseconds, 1 second = 1000 milliseconds (timestamp)
// The dt2 instance object calls the getTime() method to get the timestamp
console.log(dt2.getTime());// Milliseconds from 1970-01-01-00:00:00 to now
// Directly call the now() method of Date to get the timestamp
console.log(Date.now());
// Use the property of valueOf() method < return the Number object value of the given parameter > to obtain the timestamp
console.log(dt2.valueOf());
// particular year
console.log(dt2.getFullYear());// 2021
// month
console.log(dt2.getMonth() + 1);// 10 starts from 0, 0-11, so add 1
// date
console.log(dt2.getDate());// 30
// week
console.log(dt2.getDay());
// Hour, minute and second
console.log(dt2.getHours());
console.log(dt2.getMinutes());
console.log(dt2.getSeconds());
console.log(dt2.toTimeString());// Hour: minute: second GMT+0800 (China standard time)
console.log(dt2.toLocaleTimeString());// Hours, minutes and seconds in 12 hour system
console.log(dt2.toDateString());// English date
console.log(dt2.toLocaleDateString());// Mm / DD / yyYou can encapsulate a time expression of the style you want through the last method
function getDate(dt) {
var year = dt.getFullYear();
var month = dt.getMonth() + 1;
var date = dt.getDate();
var hours = dt.getHours();
var minutes = dt.getMinutes();
var seconds = dt.getSeconds();
// Complement
// month = month < 10 ? "0" + month : month;
// date = date < 10 ? "0" + date : date;
// hours = hours < 10 ? "0" + hours : hours;
// minutes = minutes < 10 ? "0" + minutes : minutes;
// seconds = seconds < 10 ? "0" + seconds : seconds;
function bu(i) {
return i = i < 10 ? "0" + i : i;
}
var str = year + "year" + bu(month) + 'month' + bu(date) + "day" + bu(hours) + ":" + bu(minutes) + ":" + bu(seconds);
return str;
}
// console.log(getDate(new Date()));
console.log(getDate(new Date("2022-01-01 00:00:00")));The following is a custom object that simulates the Math.max() method of the implementation system
function MyMax() {
// Method to get the maximum value
this.getMax = function() {
var max = arguments[0];
for(var i = 0; i < arguments.length; i++) {
if(max < arguments[i]) {
max = arguments[i];
}
}
return max;
}
}
var math = new MyMax();
console.log(math.getMax(1, 49, 888, 27, 75, 66));