This is the 13th day of my participation in the August More Text Challenge. For details, see:August is more challenging

Special festival, but also to continue to more text ah, I wish you a happy Chinese Valentine’s Day ohAs a mature programmer, new objects are every minute
Hello, everyone, I am circle, love the front end, like to share, thank you very much for this activity, I hope I can stick to it, thank you so beautiful, also read my article, welcome to comment area exchange and play ~

Javascript code runs in the browser

ECStack (Execute Context Stack)

Stack memory function

  • Function 1: For code execution
  • Function 2: Stores raw values and variables

EC(G)(Execution Context Global) Indicates the Global Execution Context

  • Purpose: To distinguish the environment in which the code is executed
  • Global code is executed in a global context

VO(G)(Variable Object Global) Global Variable Object

  • Stores variables declared in the current context
  • The memory in a computer, ram ROM
  • Memory: Stack memory, Heap memory
  • Running memory allocated on a memory bar [CPU]
  • Front-end performance optimization: Memory optimization

The operation of equals = assignment

1. Create a value (original value & object)
  • Raw value: find a place in the stack memory to store
  • Object: a separate heap memory space; Used to store information such as members of an object
2. Declare a variable, store the declared variable in the current context “variable object VO/AO”

  var/function/let/const/import….

3. Associate variables with Defined definitions

Object type [non-function] Assignment operation
  1. Create a heap memory space -> creates a common access address [hexadecimal]
  2. To store the key-value pairs in an object in space at once
  3. The spatial address is stored on the stack for reference to variables

Window global object

VO(G) Global variable object: Stores variables declared in a global context

Operator priority in JS developer.mozilla.org/zh-CN/docs/…

Read the underlying execution mechanism of the function in detail

Big factory interview questions know how much ~

1 / / thinking

var a = {n: 1}; //-> heap memory 0x000
var b = a;
a.x = a = { n:2}
console.log(a.x)  //undefined
console.log(b)    //

Copy the code

2 / / thinking
var x = [12.23];
function fn(y) {
    y[0] = 100;
    y = [100];
    y[1] = 200;
    console.log(y); / / [100200]
}
fn(x);
console.log(x); / / / 100,
Copy the code

Create function:

  1. Carve out a heap memory, with a hexadecimal address
  2. Stored content
  3. The code in the body of the function is stored as a string
  4. As a normal object, we also store some key and value pairs
  5. When you create a function, you declare its scope.
  6. The address of the heap memory is placed on the stack for the function name (variable) to call

Fn function execution -> execute the code string stored in the function body as code, fn(0x000) forms a new “private” execution context EC(fn) [stack execution]

An AO is also a variable Object. It is a subset of VO functions called AO, global VO, and block-level VO execution functions

1. Form a private execution context EC(…) , and then push it into the stack

    AO(…)

What to do before the function executes
  1. Initialize the SCOPE chain scope-chan

    Left: own private context Right: function SCOPE
    (fn),ec(g)>
  2. Purpose: Later in the function context code execution, encountered variables, first to see if the private,
  3. If it is not private, then look for its parent context in the scope chain… (Scope chain mechanism)
  4. Initialize this to
  5. Initialize arguments[argument set]
  6. Parameter assignment [parameter is a private variable and will be stored in all variable objects of I]

7. Variable promotion 8. Code execution

The road ahead is long; I see no ending. I will search up and down

Welcome to leave a comment ~