JavaScript omissions and supplements_javascript skills

Heap value type
Primitive type (primitive type)
Undefined: undefined (note the case: type/value, the same below)
Null: null (Undefined derived from Null)
Boolen: true/false
Number: Number.MAX_VALUE / Number.MIN_VALUE/ NaN ; isNaN() function (note: there are changes in the new version, to be checked)
String:
Type conversion:
Boolen()/Number()/String() ** refers to the type name
toString(): toString(2/8/16)
intParse()/floatParse():


Stack reference type
Predefined
Object:
Boolen:
Number: toFixed()
String: (omitted)
instanceof()


operator
delete
void Click me

label label:

Object:
An object is an unordered (different from an array) collection of name-value pairs (properties and methods)
Creation: new and {}
Extension: Adding new properties to the object (meaning in Modify the instance at runtime! ) Operator: "." or "[]"
constructor: can determine the type, but unlike typeof, it returns an object
prototype: the structure of the object

Attribute: (variable)
Scope
var: local variable, that is, the variable scope is the innermost function body

Method: (function)
JavaScript supports First-Class functions, that is, functions are treated as objects. So it can be: assigned to a variable (=), stored as an array element, used as a return value, etc.

this:
Simple memory:
Global function (function simply declared in the page): window
DOM event handler (function that handles DOM events): DOM associated with the event Element (note event bubbling)
Constructor: the instance itself

Understanding:
Normally, this always points to the object that calls the function (so-called "runtime determination")
Special cases: apply() and call(), this points to the parameter object of the above two functions

Closure:
Expression:
Function defined inside a function

Function:
Be able to read variables inside other functions
Connect the inside of a function with the outside of a function
Always keep the values ​​of these variables in memory

Array:
A An ordered (different from objects) collection of values, which can be of different types

Create: new Array() or []