Deep understanding of JavaScript functions _ Basics

Methods & Functions

Difference

1.function is a more general concept, such as math, programming

2.method is an object-oriented concept that typically appears in pairs with classes or objects

Relationship

1. The properties of an object can be any type

2. The object's property, if it is a function type, is called the method of the object

3. So the essence of the method is still the function

Call to function

1.fun ()
2.obj.fun ()
3.fun.call ()

Properties and methods of a function

1.name
2.length
3.toString

Scope

Variables are not available anywhere

Global variables (cross files)

var n = 1;
function fn () {
  console.log (n);//1
}

Local Variables (accessible only within functions)

function fn1 () {
  var n = 2;
}
Console.log (n); Uncaught Referenceerror:number is not defined

function scopes

• Functions can be independent of a scope

var n = 1;
function f () {
  var n = 2;
  Console.log (n); In the current scope of the variable search
}
f ();
Console.log (n); To search for variables in global scope

• Functions can be accessed outside the function

var n = 1;
var x = function () {
  console.log (n);
};

function f () {
  var n = 2;
  X ();
}
f ();

• Self-Invoke anonymous function

!function () {
  var n = 1;
  Console.log (n);
};

~function () {
  var n = 1;
  Console.log (n);
};

(function () {
  var n = 1;
  Console.log (n);
} ());

• Closures

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