allowing input only for float number

Why not using Regular Expression

^[0-9]*[.][0-9]+$

Read code and test here..

Regular expression would be my recommendation as well. If the value is being passed as a number and not a string you can use .toString to change it to a string and validate it with regular expression. For example:

var str = value.toString();
if(!str.match(/^-?[0-9]*[.][0-9]+$/)) {
    alert("Value must be a float number");
    return;
}
return value;

The above regex will match if the value passed is a floating point number. It accepts both negative and positive numbers. If you only want to accept positive numbers simply remove the '-?' from the expression. It will also fail if the value is simply zero '0' without any decimal point. If you want to accept zero simply add it as a condition to the 'if' statement.

You can use the above validation and an onchange event to prevent the user from entering a non-flot number.

I use this - works for keyboard input or copy and paste

$('input.float').on('input', function() {
  this.value = this.value.replace(/[^0-9.]/g, '').replace(/(\..*?)\..*/g, '$1');
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<input type="text" class="float" />

Explanation:

• First regex replaces anything that's not a number or a decimal.
• Second regex removes any instance of a second decimal.

I filter the first position input with the jQuery Caret plugin. Otherwise, once the dot is typed, it's already late to check where it was placed. I tried checking for the dot, then deleting the dot, but it does not look nice.

jQuery caret plugin: http://examplet.buss.hk/js/jquery.caret.min.js

What I did:

http://jsfiddle.net/FCWrE/422/

Try it :)

$('.filterme').keypress(function(eve) {
  if ((eve.which != 46 || $(this).val().indexOf('.') != -1) && (eve.which < 48 || eve.which > 57) || (eve.which == 46 && $(this).caret().start == 0)) {
    eve.preventDefault();
  }

  // this part is when left part of number is deleted and leaves a . in the leftmost position. For example, 33.25, then 33 is deleted
  $('.filterme').keyup(function(eve) {
    if ($(this).val().indexOf('.') == 0) {
      $(this).val($(this).val().substring(1));
    }
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.3/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/caret/1.0.0/jquery.caret.min.js"></script>
<input type="text" class="filterme">