Question

How to know that a particular input type is present or not in a div?

If I use

$("#inputId").val()

And there is no element present on this, then js gives an error.

So how could I know that the input element named inputId is present or not?

Reply me ASAP

Answer 1

You could check if

$('#inputId').length > 0

i.e. if the current selector matched any elements.

But if $('#inputId').length == 0 then $('#inputId').val() will be undefined. This is different from the scenario where the input exists, because val() would always yield a string, that is or isn’t null.

Now, you would produce an error only if you’re trying to do stuff with the value, that may or may not be undefined. For instance, the following would not work if #inputId does not exist in the DOM:

if($('#inputId').val().length > 0) { ... }

… since you’d be trying to access undefined.length. However, you could still do

if(!!$('#inputId').val()) {
    // this code will only be executed if #inputId exists, and has a value that
    // is not an empty string
}

If you’re writing form validation, it might be more useful to do

if($('#inputId').val() !== '') {
    // this code will be executed if #inputId has a value, or if it does not
    // exist in the DOM at all
}

The former condition checks that the result of .val() resolves to true, which is not the case for an empty string or for undefined. (It is also not the case for null, NaN, false or 0, but .val() will never yield any of those results)

The latter checks that the result of .val() is not exactly an empty string, which is true for an actual value, as well as for undefined.