Why doesn't it output error...WEIRD😫 and one more down the order

Question

Q1 : var name;
console.log (name); // blank screen in console

Q2 : var name=5;
// I deliberately gave it 5....I think we can

// typed in the console directly.
typeof (name); //string WHATTTTT😨
David Carroll Luis Febro 🇧🇷 Igor Makarsky daneillonge AgentSmith Anna
https://code.sololearn.com/WcLda6gMFziR/?ref=app
https://code.sololearn.com/WXDvTV8ebw11/?ref=app

Answer 1

----------
RE: Question 2
------
In order to understand what's going on here, let's first establish some context about the following code:

// <---
var name=5;
console.log(typeof(name));
// --->

1. The variable `name` refers to a property on the browser's window object: `window.name`

2. Which is proven with the lines below:

// <---
var name;
name = 5;
console.log(
name === window.name &&
name === window["name"]
) // Outputs: true
// --->

This is due to the following reasons:

a.) All global variables belong to the `window` object.

b.) Variable declarations using `var` in JavaScript are automatically hoisted to the top of the current scope.

3. The `window.name` property most likely uses a setter method to assign the string value based on the `.toString()` method of the assigned value.

- See MDN: https://developer.mozilla.org/en-US/docs/Web/API/Window/name#Notes

4. This would be similar to the following sample code:

// <---
var win = {
_name: "",
set name (value) {
this._name = value.toString();
},
get name () {return this._name;}
}

win.name = 5;

console.log(typeof(win.name));
//Outputs "string"

// --->

This mimics the same behavior as seen with `name` - a.k.a. `window.name`.

----------
RE: Question 1
------

// <---
var name;
console.log(name);
document.write(name);
// -->

The explanation for Question 2 establishes that `name` in this context is also `window.name`, which is an "empty string" value.

For this reason, `undefined` would NOT be the output for this code snippet.

Answer 2

Morpheus I agree 💯 percent.

To be honest... This question was one that almost stumped me for a few minutes until I found that vague reference in MDN.

And... of course... we don't use `var` on our team. 😉👌

Answer 3

Very interesting observation Dhinakar Reddy Challa.
Thank you for the explanation David Carroll, it makes sense now. At Mozilla there was only a short mention:-

"window.name will convert all values to their string representations by using the toString method."

But ur answer explains the overall process.

I ll just extend ur point a.

All global variables belong to window object is applicable on 2 cases.
1. When declared using var.
2. When undeclared

But global variables declared using let and const do not become a window property.

this code explores those 4 cases mentioned above.
https://code.sololearn.com/WwhKQUoMbXHH/?ref=app

Answer 4

Morpheus LOL... Yep... I was going to mention this in my original answer, but it was turning into a book already. 😂🤣

Specifically, you will see that changing `var` to `let` in both codes in the original question, the outputs for `name` are "number" and "undefined" respectively. 😉👌

Answer 5

David Carroll 😄 gotcha , I have grown scared of var. The unintended side-effects of var are so many.😵

These days I feel it's better to write code in ES6, if support for old browser is needed then we can use babel to generate old js code.

Answer 6

David Carroll yess! 💪😎

Answer 7

Dhinakar Reddy Challa
After writing that very long answer, I wonder if the following summary version would have been just as clear, or better:

TL;DR
----------
name is window.name which is always assigned the value of the toString() method.

This is why name = 5 is still a string and why console.log(name) doesn't output undefined.
------

Sadly... this summary version wasn't clear to me until after posting that much longer explanation. 🤦‍♂️🤣😂

Answer 8

David Carroll as always the man himself comes with a perfect answer..thank you David 🙏

Answer 9

'name' is not a reserved word in JavaScript but it is a DOM property so that could be the reason for the output.

Answer 10

David Carroll Morpheus Luis Febro 🇧🇷 the way the answer was build up for this question was just amazing man....we got to know more deep...thank you each one of you for answering me😊🙏

Answer 11

Dhinakar Reddy Challa I tested in the console. Everything I said is based on what the console outputted and what primitive types are. Hold on for another person's standpoint if I am wrong then. I believe your "console" is leading you astray.

P.S You do not need to downvote my answer. I did with such zeal. Furthermore, It is not my fault the facts being facts. (=

Answer 12

Morpheus tq for ur response man...u added a bit more sense to the answer🙏

Answer 13

David Carroll yea man...when I tried to console.log(window) it got a list words like a dictionary and I found name like this.....name:" "...which it is attached to global object window and is by default a string..as per your explanation 😊 thanks man

Answer 14

name is the property of window object
<body>
<script>
var mWindow=window.open("","da_wae","width=200,height=100");
mWindow.document.write("This window name is "+mWindow.name);
</script>
</body>

Answer 15

Luis Febro 🇧🇷 I placed the codes please check it buddy

Answer 16

Q1: outputs "undefined" in the console, blank screen only in the browser obviously.

Q2: No, here both syntax and output are incorrect. You need an output caller like console.log, DOM or alert.

var name = "5";
console.log(typeof(name));

This code above outputs "string" because the number is between quotation marks, thus a string. Otherwise -- in its raw form (5) -- the output would be a number.

Answer 17

Luis Febro 🇧🇷 the 1st question outputs blank in console ...undefined is not printed in the console...
The 2nd question I typed directly in the console to check the result it outputs string
even in the editor I type it outputs string...I want to give 5 to the variable name.
I request you to please review my doubt again brother

Answer 18

🤯

Answer 19

name is a window property thats why it didnt show anything change to other variable name it will log or write undefined
var a,b,c,d or whatever;

Answer 20

var nam=5;
console.log(typeof(nam));
it will give number
name is window property that stored string values thats why it gives string type.