The JavaScript sequel to the front end Obsessive Compulsive Disorder series

Tag: date () word hard disk. So Func target object component print

First, JavaScript functions 1. Common functions

function func () {}

2. Anonymous functions

SetInterval (function () {    console.log (123);},5000)

3. Self-executing functions

Most of the circumstances may introduce someone else's JS, if someone else's JS function repetition, will lead to a non-use, in order to avoid this problem, put all the functions inside the function inside. Made into a nested function.

But if the outside function name also has the repetition, how to deal with, the outside function does not have the name, and executes automatically.

How do I write a self-executing function?

  () (): First parenthesis function, second parenthesis argument. Creates a function, and automatic execution (ARG) {    

Second, JavaScript serialization and escape

• Common serialization operations

Li = [11,22,33,44]s = Json.stringify (LI)    //Convert object to String newl = Json.parse (s)    //Convert String to Object

• Escape

such as online search for a thing, the URL automatically become a% and other content

> URL = "https://www.sogou.com/web?query= time"<"https://www.sogou.com/web?query= Time ">newurl = encodeURI (URL)/Escape<"https://www.sogou.com/web?query=%e6%97%b6%e9%97%b4 ">decodeURI (Newurl)//revert to original format<"https://www.sogou.com/web?query= Time ">newurl = encodeuricomponent (URL)//Escape all<the HTTPS%3a%2f%2fwww.sogou.com%2fweb%3fquery%3d%e6%97%b6%e9%97%b4 "

The default HTTP request is not a long link, even once it is broken, but the site has to remain logged on for one months, how to achieve.

After a successful login, the website will send you a string to save it somewhere on your hard drive. This is the cookie.

Client (Cookie) = "Server side." After the data has been escaped, it is saved in a cookie

Escape ()          //To String Escape unescape ()//        to escape string decoding Urierror           //By URL encoding and decoding method thrown

Three, eval and time operation

• Eval

In Python:

val = eval ("+")    # expression exec ("Execute code")      # such as for loop. But exec just executes, no return value

In javascript:

Eval: function is a collection of eval and exec in Python

• Time operation

>  d = new Date () Mon Nov 22:46:33 gmt+0800 (China Standard Time) >  d.getminutes () 46>  n = d.getminutes () + 1258>  d.setminutes (n) 1480345113329>  Dmon Nov 22:58:33 gmt+0800 (China Standard Time)//        Date class//        var d = new Date ()   current time//        d.getxxx  get//        d.setxxx  settings

Iv. JavaScript scope 1.javascript takes a function as a scope (except let)

• Languages such as Java, C, C # are scoped with the "{}" code block.
• In Python: scopes are scoped with functions.
• JavaScript: Also a function as a scope

2. The scope of the function has been created 3 before the function has been called. The scope of the function has a scope chain and is also created before it is called

Scope chain: Nested functions, one layer at a scope

Below are three examples of what will be output separately?

Example one:            xo = "Alex";            function func () {                //var xo = ' Eric ';                function inner () {                    //var xo = ' Tony ';                    Console.log (XO);                }                Inner ()            }            func ()        //Example two:            xo = "Alex";            function func () {                var xo = ' Eric ';                function inner () {                    console.log (XO);                }                return inner;            }            var ret = func ()            ret ()        //Example three:            xo = "Alex";            function func () {                var xo = ' Eric ';                function inner () {                    console.log (XO);                }                var xo = ' Tony ';                return inner;            }            var ret = func ()            ret ()//Note: line break in browser console, use shift+ carriage return       

The scope of a function has a scope chain and is also created before being called

4. Function internal variable declaration in advance

  Example one:        function func () {            console.log (xxoo);        }        Func ();        Program Direct error        function func () {            console.log (xxoo);            var xxoo = ' Alex ';        }        In the process of interpretation: Var Xxoo;        Func ();        Undefined

Unassigned variable, declared in advance as undefined

>  var fgfundefined>  fgfundefined

V. JavaScript Object-oriented

• This refers to the object (Python self)
• When creating an object, the new function name ()

function Foo (n) {    this.name = n;    This.sayname = function () {        console.log (this.name);    }} var obj1 = new Foo (' we '); Obj1.nameobj1.sayName () var obj2 = new Foo (' Wee '); Obj2.nameobj2.sayName ()

That's fine, but there's a problem, and there's something that's been repeatedly defined, and the Sayname method is repeated in every object.

• Python object-oriented: methods are saved in class memory

Class Foo:    def __init__ (self,name):        self.name = name    def sayname (self):        print (self.name) obj1 = Foo (' we ') Obj2 = Foo (' Wee ')

• JavaScript Object-oriented prototypes:

Prototyping: Avoid wasting memory resources

function Foo (n) {    this.name = n;} The prototype of Foo Foo.prototype = {    ' sayname ': function () {        console.log (this.name)    }}obj1 = new Foo (' we '); O Bj1.sayname () Obj2 = new Foo (' Wee ');

Vi. parsing of JavaScript lexical analysis

The following code, respectively, will correspond to what output?

function T1 (age) {            console.log (age);   function age ()            var = +;            Console.log (age);            when function age () {}    //Executes because there is no call, the execution does not consider            console.log (age);        T1 (3);

Active object--> abbreviation AO
1. Formal parameters
2. Local Variables
3. function declaration expressions (higher precedence)

The following begins the analysis:

• Formal parameters:
  Ao.age = 3;
• Local variables:
  Ao.age = 27;
• function declaration expressions
  Ao.age = function ()

The analysis of the scope value can also be analyzed by lexical analysis.

The JavaScript sequel to the front end Obsessive Compulsive Disorder series