difference between global variable and window variable in javascript

Question

I am learning javascript and I am unable to understand difference between global variable and window variable and in which namespace the variables will be stored

For example,

var a = 1;
alert(window.a);

This will create alert window with message '1'.

let b = 1;
alert(window.b);

This will create alert window with message 'undefined'.

But if b is not getting created in window space, where it is getting created. When we run a javascript program, will 2 namespaces be created (one for global and one for window)?

"*will 2 namespaces be created (one for global and one for window)?*" - Yes. Although they are intertwined and a bit hard to distinguish. — Bergi, Mar 27 '18 at 15:57

axiac · Answer 1 · 2018-03-27T16:13:10.290

-1

When the JavaScript code runs in a browser, the global variables created by the user code using var are properties of the global window object.

let declares a variable that exists only in the block where it is declared.

At the top level of programs and functions, let, unlike var, does not create a property on the global object.

A block statement (also known as "compound statement") is used to group zero or more statements. The block is delimited by { and } and it can be used anywhere a single statement can be used.

edited Mar 27 '18 at 16:13

answered Mar 27 '18 at 15:50

axiac

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Not all global variables are properties of the global object. – Bergi Mar 27 '18 at 15:56
@Bergi you're right. What about now? I changed it to *"the global variables created by the user code"*. – axiac Mar 27 '18 at 16:01
A global `let b` as in the OP is still a variable created by user code. – Bergi Mar 27 '18 at 16:05

difference between global variable and window variable in javascript

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