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JavaScript JavaScript Foundations Variables Shadowing

Posted by Tony Brackins
Tony Brackins
28,766 Points

declaring a variable in a function without using "var"

I was wondering why JS lets you declare a variable in a function without using "var", then assign it to the Global Scope.

2 Answers

Zach Allan
Zach Allan
19,452 Points
Zach Allan
Zach Allan
19,452 Points

Jim warns at the end of the video that defining a variable without the 'var' keyword is a bad practice and can cause bugs in your code so I would stay away from doing that. He was just explaining what JS does by default if you assign a variable without the 'var' keyword.

Botttom line: ALWAYS assign variables with 'var' keyword. At least from what I know so far...

Michael Jurgensen
Michael Jurgensen
8,341 Points
Michael Jurgensen
Michael Jurgensen
8,341 Points

Hi Tony,

I am not sure why javascript allows you to create variables without the keyword var. However not using var can have some negative side effects. When you create a variable normally with the keyword var javascript sets a DontDelete flag to the variable. However without the keyword var the variable can actually be deleted!