What type is generally used to declare the initial value of a variable in js?

problem description

What type is generally good for declaring the initial value of a variable in

js? Why
such as
var a / / initial value, this value may be followed by a string type or a numeric type, what should I use for initialization here? 0 or""

the environmental background of the problems and what methods you have tried

var a / / initial value, which may be followed by a string type or a numeric type. What should I use for initialization here? 0 or""

related codes

/ / Please paste the code text below (do not replace the code with pictures)

var a / / initial value, which may be followed by a string type or a numeric type. What should I use for initialization here? 0 or""

what result do you expect? What is the error message actually seen?

var a / / initial value, which may be followed by a string type or a numeric type. What should I use for initialization here? 0 or""

Javascript
Mar.29,2021

js variable declaration does not necessarily need to be assigned, only const needs to be assigned when declaring, you can directly var an or let a. Assign a value when you need it. If you need a default value, it depends on the specific usage, usually an empty string "" or 0; if the variable does not need to be changed, it is recommended to use const.

depending on how you use this variable below, for numeric operations, you can give a 0 as the default value, for string concatenation, you can give a''as the default value, and if you want to use it as an array, use [] as the default value. If you assign values directly below, you can define variables above without default values.

Previous: How to replace stdout\ nin subproccess with

Next: How to get the redirection value of component mesh in forge viewer?

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-64f5-1e409c0-59919.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e409c0-59919.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?