My question is: How do I reference a dynamic 'name' of an input element in a form?

For instance, with the following HTML:

<form>
    <input type="text" name="qty1" value="input1" />
     <input type="text" name="qty2" value="input2" />
     <input type="text" name="qty3" value="input3" />

    <input type="submit" value="Submit" onClick="checkVal(this.form); return false;" />
</form>

Javascript:

function checkVal(form) {
    for (var i = 1; i <= 3; i++) {
        alert(form.qty+i.value);  // Here's where my problem is..
    }
}

The above javascript does not work. The alert is outputting NaN.

How do I reference qty1, qty2, and qty3 in a for loop using i variable?

Here's a jsfiddle: /

My question is: How do I reference a dynamic 'name' of an input element in a form?

For instance, with the following HTML:

<form>
    <input type="text" name="qty1" value="input1" />
     <input type="text" name="qty2" value="input2" />
     <input type="text" name="qty3" value="input3" />

    <input type="submit" value="Submit" onClick="checkVal(this.form); return false;" />
</form>

Javascript:

function checkVal(form) {
    for (var i = 1; i <= 3; i++) {
        alert(form.qty+i.value);  // Here's where my problem is..
    }
}

The above javascript does not work. The alert is outputting NaN.

How do I reference qty1, qty2, and qty3 in a for loop using i variable?

Here's a jsfiddle: http://jsfiddle.net/MRzWf/

• javascript
• html
• forms

• alert(document.getelementbyid('qty' + i).value); – user3272686 Commented Feb 14, 2014 at 18:44

5 Answers 5

Use Bracket notation

 form["qty" + i].value

function checkVal(form) {
    for (var i = 1; i <= 3; i++) {
        console.log("qty" + i, form["qty" + i].value);
    }
}

<form>
    <input type="text" name="qty1" value="input1" />
    <br/>
    <input type="text" name="qty2" value="input2" />
    <br/>
    <input type="text" name="qty3" value="input3" />
    <br/>
    <input type="submit" value="Submit" onClick="checkVal(this.form); return false;" />
</form>

Simply login as a dictionary

http://jsfiddle.net/MRzWf/2/

 alert(form["qty"+i].value);

Problem is form.qty+i,

To access the element of array you should used index inside the parenthesis.

There is another way to check value of input. Here is one.

  function checkVal(form) {
    var allInputs = document.getElementsByTagName('input');
    for (var i = 0; i < 3; i++) {
          if(allInputs[i].type == 'text'){
                alert(allInputs[i].value);  
          }
    }
}

DEMO

Standard Solution

Using: form.elements[] should work in all browsers..

function checkVal(form) {
    for (var i = 1; i <= 3; i++) {
        alert(form.elements["qty"+i].value);

        /* OR using dynamic name variable
        var ename = "qty"+i;
        alert(form.elements[ename].value);
        */
    }
}

Try this. It works for the above problem

function checkVal(form) {
for (var i = 0; i < 3; i++) {
    alert(document.getElementsByTagName("input")[i].value);
}  }