How to pass input field name as an argument in javascript function?

Question

I've created a JavaScript function that checks if a certain data already exists in my database. What I want to know is if there is a way to make the input field name in a JavaScript pass as an argument

Here is my code

    function checkDataAvailability(displayid,input_id,fieldname)
    {
        'use strict';
        $(document).ready(function(){
            //var x = document.getElementByName(fieldname).elements;
            $(displayid).load('php/signcheck.php').show();
            $(input_id).keyup(function(){
                 },
                $.post('php/signcheck.php', { username: form.x.value }, 
              //$.post('php/signcheck.php', { username: form.fieldName.value }, 
                function(result){
                    $(displayid).html(result).show();
                });
            });

        });
    }
    var a =  checkDataAvailability ('#userstat','#username_input','username');

A little explanation. The two commented lines are the two methods I've tried to run the field name as an argument separately. Unfortunately they aren't working.

Here is my form

<form action="php/register_exec.php" method="POST" name="form">
Username <span id="userstat" class="checkerr"></span>
<input type="text" name="username" id="username_input" required>
</form>

you can pass it as var a = checkDataAvailability ('userstat','username_input','username'); — avck
– avck, Commented Jun 5, 2016 at 3:42

avck · Accepted Answer · 2016-06-05 04:07:42Z

1

Passing form fieldnames as argument is no different than passing string argument to functions

var a = checkDataAvailability ('userstat','username_input','username');

Important thing is what you do inside the function.

You can get the value of input field in primarily two ways

Directly read the value using value property as:

document.getElementById('username_input').value

or

document.getElementById(fieldid).value //if you pass fieldid to your function

Use the form field directly

//assuming you pass formname and fieldname as variables to your function
var form = document.getElementById(formname);
var inputvalue = form.elements.namedItems(fieldname).value

You can modify them to suit your jquery syntax if need be.

answered Jun 5, 2016 at 4:07

avck

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neouser99 · Accepted Answer · 2016-06-05 04:06:32Z

0

Since you're already using the jQuery library, you can continue using it.

$('input[name="' + fieldname + '"]').val()

answered Jun 5, 2016 at 4:06

neouser99

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Gurpreet Singh · Accepted Answer · 2016-06-05 05:38:26Z

0

There are 3 ways of achieving what you desire -

If you want to stick with your current code pattern, then replacing form.fieldname with form[fieldname] would get you the correct results. This is because fieldname is a string, and form."some string" would give you an error.
The other two ways are the same as neouser99 and avck specified in their answers.

answered Jun 5, 2016 at 5:38

Gurpreet Singh

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