JS executes code

Why does this code report an error?

Javascript
Mar.21,2021
What does the expression

var x = xx; do? He first declares a variable in memory, where the variable is not processed, so the value is undefined, and then assigns the result on the right to the variable on the left.

in your example, first declare a variable obj, in memory, and then look on the right, and on the right is an object, so it opens up a space in heap memory to save the object, and when it reads name:'js' , it assigns a value to the name attribute of the object. When reading to the next line, because the can attribute corresponds to an immediate execution function, you will get the value of the function first. Then assign a value to the can property, so what is done in this function? This function first prints obj, when obj has just been declared and has not been assigned yet, so an error is thrown when reading the next line obj.name for undefined,.

clipboard.png

< H2 > you want to achieve this, right? < / H2 >

closure 

  var obj = function () {
        var name = 'js';

        var dofun = function () {

        };
        return can = (function () {
            // console.log(obj);
            return name;

        })();
    }
    console.log(obj(), '1');

class writing 

class OBJ {
        constructor() {
            this.name = 'js';
        }

        can() {
            return this.name;
        }


        do() {


        }
    }
    var ob=new OBJ()

    console.log(ob.can(), '2');

Previous: How to add known header information to the method of get in angular4

Next: About list derivation in Python

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
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1eafeec-5d0b1.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1eafeec-5d0b1.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?