javascript data format (four) of the object basis functions ---

First, the definition of the function

　　Functional block period can be reused

 

1.1 function declaration and function expression

　　Defined functions commonly used in two ways as a function declaration and function expression, as follows:　　

　　　　function fn1 () {// function declarations
　　　　　　the console.log ( 'Fn1 ()')
　　　　}
　　　　var Fn2 = function () {// expression
　　　　　　the console.log ( 'Fn2 ()')
　　　　}

About the difference between function declarations and function expressions, the god of reference: https://www.cnblogs.com/chaoyuehedy/p/9110063.html

 

1.2 function calls

　　Function calls in the following ways:

• Direct call: test ()
• By calling the object: obj.test ()
• new calling: new test ()
• Let become interim test method of obj call: test.call/apply (obj)

 

1.3 callback function

　　Simple to understand what function is a callback function?

• You define
• You do not tune
• But in the end it is executed (at a certain time or a certain condition)

Common callback function:

• dom event callback function ==> events dom element
• Timer callback function ===> window
• ajax request a callback function
• Lifecycle callback function:

1.4 IIFE (immediately execute the function)

　　Full name: Immediately-Invoked Function Expression, namely immediately execute the function. Commonly written as:

　　　　(function () {// anonymous function call from
　　　　　　var. 3 A =
　　　　　　the console.log (A +. 3)
　　　　}) ()

The above is understood as (anonymous function) (), i.e. directly after a defined function anonymous () to call the anonymous function. More knowledge about the immediate execution of the function, refer to: https://www.cnblogs.com/cnfxx/p/7337889.html

 

Perform the function of the left and right immediately:

• Hidden achieve its internal variables are not visible outside (local function variables scope as a function of the body), is a variable safer
• Does not pollute the external (global) namespace, the internal variables local variables, global variables will not cause changes
• It is used to encode module js

 

1.5 Functions of this

What 1.5.1 this that?

• Any function essentially invoked by an object, that is, if not directly specified window

• All internal functions have a variable this
• Its value is a function of the current object call

1.5.2 How to determine the value of this? 　Remember the following points

• test(): window
• p.test(): p
• new test (): newly created objects
• p.call(obj): obj

　　Learn more about JavaScript this, please refer to: https://www.cnblogs.com/yuanbo88/p/6290543.html