I'm currently playing around with "const" variable in javascript and here is my code

My question is, why is "const x" undefined when used with "console.log", but it is defined when used on its own?

p.s. -- I understand that both global "const, let" do not bee the property of "window" object, unlike global "var". But I am unsure as to whether this played any role in the code above.

I'm currently playing around with "const" variable in javascript and here is my code

My question is, why is "const x" undefined when used with "console.log", but it is defined when used on its own?

p.s. -- I understand that both global "const, let" do not bee the property of "window" object, unlike global "var". But I am unsure as to whether this played any role in the code above.

• javascript
• scope
• constants

• Possible duplicate of Chrome/Firefox console.log always appends a line saying undefined – Randy Casburn Commented Jan 18, 2019 at 2:35

2 Answers 2

You're seeing undefined because console.log() function actually returns you that.

Notice how x is still 123 when you query just x?

The assignment operation for const x = 123; is undefined because it returns you undef as well.

What browser/version are you using? Trying it in both FF65 and Chromium71, console.log( x ); indeed gives me 123 ...