Assign value to html element using javascript - Stack Overflow

I have this function getOrderNumber() that I want to create a unique order number using the javascript getTime(). I need then the function getOrderNumber() to somehow assign a value to the html element. I tried a few iterations of what I have here which didn't work.

Any help would be appreciated.

<form action="/saocctest.cgi" method="post">

<!--get unique order number-->
<script>
function getOrderNumber() {
    var d = new Date();
    var n = d.getTime();
    form.elements("orderNumber").value=n;
}
</script>

<input type="hidden" name="orderNumber">

I have this function getOrderNumber() that I want to create a unique order number using the javascript getTime(). I need then the function getOrderNumber() to somehow assign a value to the html element. I tried a few iterations of what I have here which didn't work.

Any help would be appreciated.

<form action="https://www.someurl/saocctest.cgi" method="post">

<!--get unique order number-->
<script>
function getOrderNumber() {
    var d = new Date();
    var n = d.getTime();
    form.elements("orderNumber").value=n;
}
</script>

<input type="hidden" name="orderNumber">

• javascript
• html
• function

Share Improve this question Follow edited Feb 8, 2023 at 5:53 Elijah M 8771111 silver badges2424 bronze badges asked Sep 15, 2016 at 21:31 got2bgot2b 3911 gold badge11 silver badge88 bronze badges 1

• Seems like you need to do a bit more study. I'm not sure what you're really trying to acplish here. What's calling your function? Where did the variable form e from? Maybe this will help: w3schools./js/js_htmldom_html.asp – OneHoopyFrood Commented Sep 15, 2016 at 21:36

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3 Answers 3

Sorted by: Reset to default 1

Set Id name to your HTML form

<form id="myForm" action="https://www.someurl/saocctest.cgi" method="post">

And then assign the value using this in your function

document.getElementById("myForm").elements[0].value = 'hello';

Or else add id/class to your input and the assign using

document.getElementById('id'); // Using Id
document.getElementsByClassName('class')[0]; // Using class

It will work

Demo : https://jsbin./molagu/2/edit?html,js,output

JavaScript doesn't create global references of HTML page elements in this way. In modern browsers, if you've a element with specific identifier, you can directly get it from its id in the global object.

For example

<div id="my-id"></div>

JS

alert(this['my-id'])

Where this, window, if you're not in strict mode and if you're in a global scope.

Actually, if you want a cross-browser equivalent way to get the form element,

document.getElementsByTagName('form')[0]

Every DOM element has methods like getElementsByTagName, getElementsByClassName, (these return a HTMLCollection, looks like a array, but it's not) ...

The document is the one object that contains the getElementById method, which returns the first element with specific identifier.

Also, if you want to get your form elements, use the methods I quoted, or simply index the form reference with the 'name' attribute of the specific child. It's cross-browser to use HTMLElement().getElementsByTagName, etc.

---

Only input elements has the value property. You can change the innerHTML or innerText instead (they're getters/setters);

I think this is what you're after

<form id="myForm" action="https://www.someurl/saocctest.cgi" method="post">

<script>
function getOrderNumber() {
    var myForm = document.getElementById('myForm'); 
    var d = new Date();
    var n = d.getTime();
    myForm.elements[0].value = n;
}
</script>

<input type="hidden" name="orderNumber">

Notice you could probably just give the input an id and change the value that way e.g.

<input type="hidden" name="orderNumber" id="myOrderNumber">

then

document.getElementById('myOrderNumber').value = n;

Also note when using document.getElementById("myForm").elements[0].value = 'hello';as per other answers here that you are targeting the first element within the form, if you ever add another element above this then you will update the wrong item value.

Safest option as I've mentioned would be to place an id on the input itself then target that.