Function declarations, call parameters, return, the recursive

JavaScript function

To achieve a particular function code segments together, code blocks can be reused.

Pros: make the program simpler and more logical conditioning calling more convenient and easier to maintain

Function declaration

• The basic syntax
  
  function 函数名（[形参1，][形参2，]......）{ //函数体 [return//返回值] }

  Before and after the declaration can be called

• Arguments (anonymous function)
  var 变量=function([形参1，][形参2，]......){ //函数体 [return//返回值] }

  After the declaration calls

Function is called

• Function name (); variable name ();
• Behind the event call

• Since calls
  
  (function () {alert (1 )}) ()

  Function overrides the self-declared variables function, to be called after the basic syntax of a function declaration statement, the statement can be called before and after the declaration

parameter

Dynamically change the function of the internal variable and the different results obtained with such a function thereof.

• Parameter

  () Function declaration inside the value when the value of the argument to accept

• Arguments

  When the value inside the function call (), the parameter assignment to

Parameter Description

• Parameter can be any data type

arguments object

In the object function inside the hermit created

Properties:
length
callee
access parameters passed specific values. arguments [index]
console.dir print object to the console

Function overloading

• arguments get arguments

  Different number of parameters or different types of parameters, so that a function of different functions

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Scope of a function

Global Variables

在页面的任何地方都能访问到的变量，拥有全局的作用域

1. The outermost layer of the variables defined functions
2. There is no direct variable assignment with Global Properties

Local variables

只能在固定的代码片段中访问到

1. Variables defined inside the function;
2. Parameters are also local variables

return

To a function returns a value, and terminates the current function out

return return value

1. The return value can be any data type
2. You can only return a return value
3. If no return value, the default value is undefined

recursive function

It calls itself inside the function