So, for applying decimal only validation in js we will use onkeypress event of input boxes. So you can check the below code for applying the validation.

Below is a code in HTML and JavaScript to Number And Decimal validate a text field

<form>
    <div class="form-group row">
        <label for="inputPassword" class="col-sm-2 col-form-label">Enter Only Number And Decimal</label>
        <div class="col-sm-10">
            <input type="text" class="form-control" id="inputNumberWithDecimal" placeholder="Enter Only Number And Decimal" value="" name="inputNumberWithDecimal" onkeypress="return onlyNumberWithDecimal(event)" />
        </div>
    </div>
</form>

Here is how to validate the input only to accept Number And Decimal this will only take Number And Decimal values like "12.5"

<script>
    function onlyNumberWithDecimal(evt) {
        try {
            var charCode = (evt.which) ? evt.which : evt.keyCode;
            if (charCode != 46 && charCode > 31
                && (charCode < 48 || charCode > 57))
                return false;

            return true;
        }
        catch (err) {
            alert(err.Description);
        }
    }
   
</script>

You can copy complete code from here .

<form>
    <div class="form-group row">
        <label for="inputPassword" class="col-sm-2 col-form-label">Enter Only Number And Decimal</label>
        <div class="col-sm-10">
            <input type="text" class="form-control" id="inputNumberWithDecimal" placeholder="Enter Only Number And Decimal" value="" name="inputNumberWithDecimal" onkeypress="return onlyNumberWithDecimal(event)" />
        </div>
    </div>
</form>
<script>
    function onlyNumberWithDecimal(evt) {
        try {
            var charCode = (evt.which) ? evt.which : evt.keyCode;
            if (charCode != 46 && charCode > 31
                && (charCode < 48 || charCode > 57))
                return false;

            return true;
        }
        catch (err) {
            alert(err.Description);
        }
    }
   
</script>

So, this is how you can apply decimal only validation in javascript.