Check if input value is empty and display an alert

Question

How is it possible to display an alert with jQuery if I click the submit button and the value of the input field is empty?

Answer 1

Better one is here.

$('#submit').click(function()
{
    if( !$('#myMessage').val() ) {
       alert('warning');
    }
});

And you don't necessarily need .length or see if its >0 since an empty string evaluates to false anyway but if you'd like to for readability purposes:

$('#submit').on('click',function()
{
    if( $('#myMessage').val().length === 0 ) {
        alert('warning');
    }
});

If you're sure it will always operate on a textfield element then you can just use this.value.

$('#submit').click(function()
{
      if( !document.getElementById('myMessage').value ) {
          alert('warning');
      }
});

Also you should take note that $('input:text') grabs multiple elements, specify a context or use the this keyword if you just want a reference to a lone element ( provided theres one textfield in the context's descendants/children ).