access form elements in java script dynamically

Question

i need to get one of the form variables dynamically in my javascript function, which takes the parameters of form and element name to be accessed in that form.

Say, i will be calling on some button click like this onClick="javascript:init(this.form, 'USERNAME')"

If i do it as : document.getElementById(formName).USERNAME.value. This works. But, i dont have to give the element name directly. I want to read it from the passed arguments.

So, if i do it as below: document.getElementById(formName).elem.value - this gives an exception saying cannot get value of undefined

function init(form, elem){
            try{
                var formName = form.name;
                var elementValue = document.getElementById(formName).elem.value;
                ..
            }catch(e){
                alert(e.message);
            }                           
        }

Kindly suggest me. How can i get the passed elem value. Thanks in advance!

It should probably be var elementValue = document.getElementById(formName)[elem].value; — Jeff Shaver
– Jeff Shaver, Commented Feb 3, 2014 at 12:56

Oleg · Accepted Answer · 2014-02-03 13:04:09Z

1

In your case in order to access properties of an object you can use the following notation:

something[elem].value

Consider the following code:

var prop = "a",
    obj = {a: 1};

obj.a === obj["a"] === obj[prop];

Then your code will look like:

function init(form, elem){
    try {
        var formName = form.name,
            elementValue = document.getElementById(formName)[elem].value;
            // ...
        } catch(e) {
            alert(e.message);
        }                           
    }
}

edited Feb 3, 2014 at 13:04

answered Feb 3, 2014 at 12:58

Oleg

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Comments

sughan90 · Accepted Answer · 2014-02-03 13:00:37Z

1

Make a button to pass the value to the javascript. The button will get the value(ex: from textbox) and will pass it to the javascript.

So,

<input name="textbox1" id="textbox1" type="text" />
<input name="buttonExecute" onclick="init(document.getElementById('textbox1').value)" type="button" value="Execute" />

answered Feb 3, 2014 at 13:00

sughan90

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1 Comment

Anita Over a year ago

Yes sughan90, your suggestion makes sense. I will follow the same. Thanks!

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