Global variable not working as an input value

Question

I am a JavaScript beginner, I am stuck with a problem regarding variables.

I wrote this code :

var acNo = document.getElementById("ac").value;

function doSomething(){
    alert(acNo);
}

The output is: undefined

But when I did this :

var acNo = 3

The output is 3

Html code : (This is a very big project so that's why I cant share much code, but I am sharing the HTML code related to this script)

<td>A/c</td>
            <td> <input type="number" name="" id="ac"></td>
            <td> <input type="number" name="" id="acHour"></td>

Can you please tell me how can I fix it while keeping the variable global only.

You will have to show your HTML too, mate – Tushar Shahi Mar 27 '22 at 10:00 — Tushar Shahi, Mar 27 '22 at 10:00
I have edited the question and put the code too – Vinayak Handa Mar 27 '22 at 10:10 — Vinayak Handa, Mar 27 '22 at 10:10

score 1 · Answer 1 · answered Mar 27 '22 at 10:20

Try defining acNo after the document has fully loaded, or within the function.

Solution 1:

let acNo;

window.onload = () => {
 acNo = document.getElementById("ac").value;
}

function doSomething() {
 alert(acNo);
}

Solution 2:

funtion doSomething() {
    alert(document.getElementById("ac").value)
}

score 0 · Answer 2 · answered Mar 27 '22 at 10:03

A way you can go to check that is by opening the dev tools of your browser and running your document.getElementById in the console.

You will be able to see everything about the element and what properties it has. For example, you might want to check innerHTML instead of value depending on your element type.

score 0 · Answer 3 · answered Mar 27 '22 at 10:14

0

I think the value is only set in the beginning and not when you run doSomething later. If you want to have the value globally, have a global variable and keep updating it when you call doSomething.

var acNo = document.getElementById("ac").value;

function doSomething(){
acNo = document.getElementById("ac").value;
alert(acNo);
}

answered Mar 27 '22 at 10:14

Tushar Shahi

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Is there any way to use the variable without assigning it in the function scope? – Vinayak Handa Mar 27 '22 at 10:18
Then you have to listen to the change of the input value. Using the attribute `onChange`. Like : https://stackoverflow.com/questions/55033836/how-do-you-listen-detect-changes-to-an-input-value-when-the-input-value-is-c – Tushar Shahi Mar 27 '22 at 10:20
But that is something you can find on SO easily. – Tushar Shahi Mar 27 '22 at 10:20

Global variable not working as an input value

3 Answers3