Self executing function

/*
             Self executing functions 
            +  Immediate execution function 
            +  That is, the function calls itself , After the function declaration , I will execute it immediately 
            +  characteristic ：
              =>  When the function is finished , It will be destroyed in the memory space , Save space than ordinary functions 
              =>  When we use self executing functions , Will form a private scope , Only for internal use , It can't be used in other places outside 
            +  effect ：
              =>  Suitable for doing some page initialization things   
              =>  Suitable for making page file modules , Prevent conflict problems 
            +  Page modular history 
              =>  The technology was not mature before , The front end is just in its infancy , There is no better module solution , There are many back-end personnel also doing the front-end 
              =>  People are in the process of development , I found that the front end didn't even feel special about the module low, So they worked together , It is proposed to use self executing functions as modules 
              =>  Self executing functions do front-end module business , Use for seven or eight years , It was not until its own module appeared in the front end that it was gradually not used 
            +  Be careful ：
              =>  When the self executing function is connected with another bracket, an error will be reported , I will execute two sentences of code as one sentence 
              =>  Set a semicolon in front of our self executing function , Can solve this problem     
        */

        // Recommend this style of writing 
        // (function(){
    
        //     console.log(' I'm a self executing function , to see somebody for the first time , Please understand !')
        // })()

        // function fn(){
    
        //     console.log(123)
        // }
        // fn()
        // console.log(fn)

        // let fn = (function(){
    
        //     console.log(123)
        // })()
        // console.log(fn)

        // Self executing functions can also be written like this 
        // (function(){
    
        //     console.log('hello')
        // }())

        console.log(' This is a function ')
        ;(function(){
    
            console.log(' Self executing functions ')
        })()

 Page function module 
<script src="js/a.js"></script>
    <script src="js/b.js"></script>
    <script>
        // Be careful 1： If using let Declared variables , If the variable names are the same , Will report a mistake , Say we num Variables have been declared 
        // console.log(num)

        // Be careful 2： If using var Declared variables , If the variable names are the same , The back will cover the front 

        console.log(modA.num)
        console.log(modB.num)

        modA.slider()
        modB.cart()

    </script>


a.js
;(function () {
    
    console.log(' This is the carousel map module ')
    // Custom subscript 
    let num = 0
    // var num = 0
    function slider() {
    
        console.log(' This is the business logic code of the rotation chart ')
    }
    // We can use what we need for the outside world , Can be placed in window On 
    window.modA = {
    
        num,
        slider
    }
})()


b.js
;(function () {
    
    console.log(' This is the shopping cart module ')
    // Custom subscript 
    let num = 1
    //var num = 1
    function cart() {
    
        console.log(' This is the logic code of shopping cart ')
    }
    window.modB = {
    
        num,
        cart
    }
})()