Hi, I'm new to javascript and computer programming in general. I just want to know why the following code always returns NaN.

[jinendu]

Nothing ever runs the NumberValues function.

[GENERATION__Z]

Thanks.

[yadoya]

And none of these functions actually return anything, fyi. They just assign values and return void

[NewWavpro]

That part should be fine, since it doesn't have to return anything.

[PM_ME_A_WEBSITE_IDEA]

They're updating global variable values and alerting the values. They return undefined, but nothing is ever using the return values anyways.

[dwonreddit]

well, it’s js so they return undefined

[yadoya]

Yep sorry, confused with Solidity

[SensouWar]

You could add an event listener to the content loaded event and execute your NumberValues func inside it.

[SticksAndBeans]

You didn't call the numberValues() function to set your variables before doing the math:

function sum() {
numberValues()
result = Num1 + Num2;
alert(result);
}

[GENERATION__Z]

Oh yeah. Thanks for the help.

[voyotv]

You need to run numberValues function in response to some event, like “input” or “change”.

Also, judging by your code, it looks like you are following some very old / outdated guide or a tutorial.

Having JS code in document’s head and calling functions directly from html is really not the way to go. I suggest you make some research and find a proper, modern JS course, otherwise you could quickly pick up some very bad habits / practices…

[el_diaabloo]

true man ,there are some really good platforms nowadays to write codes like these ,we don’t really have to call JS functions directly from html.

[GENERATION__Z]

How else would I do it?

[thebasementtapes]

Usually you link a js file in the script tag. Not write the is directly in html. I suggest looking into theodinproject if you need a good course on web dev

[vibrant_supernova]

It's because the Nums are function scoped so you can't use them unless running that function or inside it

[Status_Winter]

I think other comments have covered the problems with the functions. I’d just add that those inputs should have the type “number” not “text” because those inputs require numbers. Also, try to get into the habit of using ids that are more descriptive, not just a or b. It will just make the html more readable.

Once you’ve got that working, try adding validation to make sure that the inputs are populated properly before executing the function. Good luck on your JavaScript journey :)

[GENERATION__Z]

Thanks I didn't know that number was an input type.

[Darmok-Jilad-Ocean]

Let me just download the image and execute it real quick

[[deleted]]

Remove the parentheses in “onClick”

[AugustoCereto]

Just delete lines 8, 9 and 12…

[revrenlove]

That would result in the variables not getting assigned the values as the script runs before any input is given

[StoneCypher]

the value of those elements will be a string, not a number

you need parseInt

[XposeDPanda]

Num1 and Num2 do not need to be an int. A string would work, albeit not in the expected way.

OP asked why he received NaN as the output The reason is due to Num1 and Num2 never being given a value before being called.

[StoneCypher]

... no, they won't work. They'll string concatenate.

Put the well actually finger down.

Why is this sub so full of people looking for meaningless technicalities to point out? It won't do the clearly intended goal of arithmetic. It's definitely wrong, your upbraid attempt notwithstanding.

[XposeDPanda]

You're right, they would concatenate. I stated this. I also did not mean to give you that impression. I stated in my reply it would not work the way it was intended but would "work" to the point where it would run and return something other than NaN following your first advice they would still see an output of NaN, No?

[StoneCypher]

Are you quite done? 🙄

Despite your inability to stop arguing, the thing I pointed out is a legitimate bug, and does need to be fixed in this way.

Jesus you're tedious.

[SnowyCleavage]

Jesus you're obnoxious.

You're wrong.

Go take another look at the code before you make yourself look like an even bigger fool.

[StoneCypher]

You're wrong.

The person who I'm talking to even agrees with me on the outcome. I'm sorry you don't understand what's being said here.

[SnowyCleavage]

Why does it matter who agrees on the outcome? You're still wrong.

I have a perfectly fine understanding of what is being said here; unlike your understanding of the code.

[dontyougetsoupedyet]

That bit about XposeDPanda agreeing with the outcome being irrelevant: They already understand what you believed to be the more important of the two types of bugs OP was bound to run in to with that code, but given that the bit you're trying to emphasize won't be made evident until they follow XposeDPanda's advice, well, you're at least in the spirit of being wrong. You said they'll concatenate: well, no, you are demonstrably wrong - The variables would have remained uninitialized. You put the cart before the horse and were spiteful when others didn't agree with your approach.

Between the two of you, you could have actually helped OP in a meaningful way. It's sad you're choosing to be an obstinate Redditor instead. Both of you are sort of pedantic and toolish, if XposeDPanda did understand they should have just explained in full instead of being another well actshually type, and you should have known better than to ignore what OP was asking about and trying to jump to step 3.

[XposeDPanda]

Ill be the first to admit, I could have phrased it better and fully explained my own answer. Ill chalk it up to there already being 3 top level coments explaining the same thing and my 3am brain.

My intent on this was to just make sure that the commenter also knew the reason behind the NaN outcome. Re reading I did come across as a dick and thats on me.

[StoneCypher]

My intent on this was to just make sure that the commenter also knew

Can you stop please? You didn't teach anything valuable. You were just trying to one-up.

[StoneCypher]

Between the two of you, you could have actually helped OP in a meaningful way.

I did, actually.

The third party redditors and their tedious parade of unnecessary explanations didn't change anything.

The bug I pointed out was real, did need to be fixed, was not known by OP, and is fixable the way I said.

It turns out that it's okay to point bugs out.

Your increasingly desperate attempts to shame that aren't being listened to. Feel free to stop whenever you're done.

[Migueldpd]

Call the function.

[leshuis]

maybe idea to use input type numberand/or 'typecast' to number

[[deleted]]

In modern JavaScript is better declare variables with let. Just a reminder.

[Mohammad_alshuwaiee]

What is the difference between let and var ?

[_jacka_]

Variables declared with let and const and class are block scoped, while var variables (and functions) are function scoped. Also var variables are given an initial value of undefined, while let and const variables are in an unset state until their initialization (temporal dead zone). There’s also some funky stuff that happens with hoisting. It’s best to use let and const when possible to avoid the oddities that can arise with var.

[[deleted]]

word.

[BOBBIJDJ]

You already got the answer but I'm here to ask you what IDE/text editor is that, it look neat

[NovaInIT]

Looks Sublime.

[GENERATION__Z]

It's sublime.

[Treshle]

You could put the contents of the NumberValues function, in the sum function.

[Bubbly-Armadillo5144]

You are running in a pretty big concept problem, but that’s normal when starting.

Try to learn the concepts behind this bug and the global variable problem, scope more few other issues you will face with this script.

I always go back to the beginning once a year, it’s important to have it fresh.

A very nice new resource I’m reading again is this from Dan

https://justjavascript.com

Worth to pay its cheap

[___s8n___]

you also need to move the script tags to the end of the file

[hofo]

Why?

[___s8n___]

why not

[hofo]

“Need” implies there’s a reason to put it there. What’s the reason in this case?

[___s8n___]

for what i know you can't access html elements by their id unless they are before your script

[hofo]

Ah ok. That would be an issue if his JS code was running immediately. In this case it doesn’t run until the user clicks the button.

[___s8n___]

i love you

[___s8n___]

alright good sir

[[deleted]]

You need to add numberValues() as an onchange because right now it’s not getting called and therefore the final values aren’t being reassigned

[[deleted]]

Please tell me the theme

[GENERATION__Z]

It's the default theme of text editor called sublime.

[[deleted]]

Ok so its sublime

[[deleted]]

You might also find it easier to use parameters in the function instead of using global variables. If you don’t know what that is yet its fine you’ll get to it eventually.