The problem of running order of javascript function

  • 1 
    function a() {
        console.log("1")
    }
    a()
    (function () {
        console.log("2")
    })();

after running

clipboard.png

  • 2 
    a()
    function a() {
        console.log("1")
    }
    (function () {
        console.log("2")
    })();

if you do this, you won"t get an error, but of course you won"t get an error if you delete the function that executes immediately.
what is the reason for this?

Javascript
Feb.27,2021

add a semicolon 

function a() {
        console.log('1')
    }
    a();
    (function () {
        console.log('2')
    })();

the semicolon is automatically inserted in the wrong position. It should be parsed as follows. Just add a semicolon a (); . 

   function a() {
        console.log('1')
    }
   a()(function () {
        console.log('2')
    })();

is missing a semicolon.

standardize writing 

function a() {
    console.log('1')
};
a();
(function () {
    console.log('2')
})();

because the semicolon is missing, followed by parentheses, the first one is identified as 

 a()(function () {
        console.log('2')
    })();

so an error is reported (in this case an is expected to return a function), and then call with an anonymous function as an argument and then return a function before execution.

Previous: The official account of js Wechat has modified the code.

Next: Workerman's chat transcript

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
© 2021 CodesHelper
Advertising Contact us About us
Menu