06 MU class Network "Attack on node. JS Foundation (i)" Scope and context

Scope

Ability to invoke a function to access a variable

//Global VariablesvarGlobalVariable = ' This is global variable '//Global Functionsfunctionglobalfunction () {//Local Variables    varLocalvariable = ' This is local variable 'Console.log (' Visit gloabl/local variable ') Console.log (globalvariable) console.log (localvariable) globalvariable= ' This was change variable 'Console.log (globalvariable)//Local Functions    functionloaclfunction () {//Local Variables        varInnerlocalvariable = ' This is inner local variable 'Console.log (' Visit gloabl/local/innerlocal variable ') Console.log (globalvariable) console.log (localvariable) Console.log (innerlocalvariable)} //Accessible local functions within a scopeloaclfunction ()}//local variables and functions cannot be accessed globallyGlobalfunction ()

Context

Related to the This keyword, is a reference to an object that invokes the current executable code

This points to the function owner and can only be used in functions

This points to the constructor function

var pet = {    words:' ... ' ,    speak:function() {        Console.log (this. Words)        Console.log (  This = =pet)    }}pet.speak ()

This points to the global object

function Pet (words) {    this. Words = words    console.log (this. words)    Console.log (this = = Global)}//This points to the global globally object Pet (' ... ')

This points to the instance object

function Pet (words) {    this]words = words    thisfunction() {        Console.log (this. words)        Console.log (this)    }}  varNew Pet (' Miao ') cat.speak ();

Using call and apply to change the context reference object this points to the object referencing the method

var pet = {    words:' ... ' ,    speak:function(say) {        this. Words)    }}pet.speak (' haha ‘)

Using call-apply

var pet = {    words:' ... ' ,    speak:function(say,free) {        this. Words    }}var dog={    words:' Wawa '}pet.speak.call (dog,' haha ', ' lala ') pet.speak.apply (dog, [' haha ', ' lala '])

Use call and apply for inheritance convenience

function Pet (words) {    this]words = words    thisfunction() {        Console.log (this. words)    }}//Dog Inherits Pet, owning the Speak method of Pet function  Dog (words) {    Pet.call (this, words)}varNew Dog (' Wawa ') dog.speak ()

06 MU class Network "Attack on node. JS Foundation (i)" Scope and context