深入理解JS notes |　青训营笔记

basic concepts

birth

similar to C syntax
Java datatype and memory control
Function is the first class
prototypec inheritance

Develop

Mocha => Livescript => Javascript Why use ECMAScript ? Because MS used Jscript. in practice ECMAScript === js

JS Fundamental

single threaded
dynamic and weakly typed
object-oriented functional parameter => outcome //jQuery
interpret the class language
safty

Data Type

Reference type

const a.name ='zq';
const b = a;
console.log

Complex data type in JS can be changed (tdeclared with const) The base data type assignment is the value and CANNOT be changed

Scope

ES5	ES6
global function	++block

Variable Boost visit a variable before it is declared with const or let will cause Error var will cause Undefined function can be called before defined

how does js run

why byte code first?

to reduce memory cost

What is JIT a code appears twice or more , V8 will consider it as 'hot code' and transform it into machinecode.

what is "execution context"

variable env
lexial env
this
excutable code

What are they
- Global only one in a life. At the bottom of the call stack . attention the stack overflow
- Function
创建执行上下文的时候做了什么?
- 绑定this
- 创建词法环境
- 创建变量环境
- 词法环境: let const
- 变量环境： var
- Outer:指向外部的指针 (This part is not fully understood)
实现了栈中垃圾回收

advanced tips

闭包/Closures

add==>in heap, memory not recycled

this

in Function , this => global/window
what about object

const name = 11;
const obj = {
    name: 'wq',
    showName(){
        console.log(this.name)
    } 
}
obj.showName()

apply,call,bind

Constructor

创建临时对象
ｔｈｉｓ指向对象
执行构造函数
返回临时对象

heap & stack

heap

新生代 /小
- 对象区域　
- 空闲区域
老生代（主垃圾回收器
- 1. 标记清除　
  2. 内存整理
- 由新生代进入
- 清除后内存不连续
耗时问题

Events Loop

之前不太懂

then 微任务，先于宏任务

What about Node?

summary

最后，为什么前半段笔记用英文：因为没装好输入法（汗，用的Ubuntu22.04,如果有好的输入法欢迎推荐如果有单词拼写错误请指正

标题只是课程名称，我还不敢说理解JS

Events Loop 部分还不甚理解

深入理解JS notes | 青训营笔记