make an input only-numeric type on knockout

Question

i read many tutorials but i dont know how to do this, this is the input

input(type=\"text\",name=\"price\",id=\"price\"data-bind=\"text: price,valueUpdate:[\         


        

Answer 1

Knockout has extenders for this. Check This from knockoutjs.com explaining how to use observable extenders to force input to be numeric. I paste the code from the documentation here:

Source code: View

<p><input data-bind="value: myNumberOne" /> (round to whole number)</p>
<p><input data-bind="value: myNumberTwo" /> (round to two decimals)</p>

Source code: View model

ko.extenders.numeric = function(target, precision) {
    //create a writable computed observable to intercept writes to our observable
    var result = ko.pureComputed({
        read: target,  //always return the original observables value
        write: function(newValue) {
            var current = target(),
                roundingMultiplier = Math.pow(10, precision),
                newValueAsNum = isNaN(newValue) ? 0 : parseFloat(+newValue),
                valueToWrite = Math.round(newValueAsNum * roundingMultiplier) / roundingMultiplier;

            //only write if it changed
            if (valueToWrite !== current) {
                target(valueToWrite);
            } else {
                //if the rounded value is the same, but a different value was written, force a notification for the current field
                if (newValue !== current) {
                    target.notifySubscribers(valueToWrite);
                }
            }
        }
    }).extend({ notify: 'always' });

    //initialize with current value to make sure it is rounded appropriately
    result(target());

    //return the new computed observable
    return result;
};

function AppViewModel(one, two) {
    this.myNumberOne = ko.observable(one).extend({ numeric: 0 });
    this.myNumberTwo = ko.observable(two).extend({ numeric: 2 });
}

ko.applyBindings(new AppViewModel(221.2234, 123.4525));

Answer 2

 <input type="text" id="alpha-validation" data-bind="value: YourDataName, valueUpdate: 'afterkeydown' , event: { 'input': AlphaCheck}" style="text-transform:uppercase">

create AlphaCheck Function and add that.

    $('#alpha-validation').keyup(function () {
        if (this.value.match(/[^0-9 ]/g)) {
            this.value = this.value.replace(/[^0-9 ]/g, '');
        }
    });

That will works!

Answer 3

An alternative approach: I have found that Knockout works well in combination with jQuery-validate. You just need to make sure that you validate the form before you attempt to use the numeric value.

Say you have a form DOM element, you can set up validation rules via

$(".yourform").validate({
    rules: {
        year: {
            digits: true,
            minlength: 4,
            maxlength: 4
        }
    },
    messages: {
        year: "Please enter four digits (e.g. 2009).",
    }
});

In your viewmodel you set the two-way binding up as usual, e.g. via self.year = ko.observable(""). Now make sure that you call $(".yourform").valid() before you are further processing self.year(). In my case, I am doing var year = parseInt(self.year(), 10). Right after form validation this is expected to always produce a meaningful result.

Answer 4

We can restrict user to input user more than two decimal number Ex. 23.81, 3452.83 Modified code is as below. The reference code is taken from the @Martin Surynek answer.

HTML -

<p>
    <input data-bind="value: myNumberOne" /> (round to whole number)</p>
  <p>
    <input data-bind="num, value: myNumberTwo" /> (round to two decimals)</p>

Script -

<script>
    ko.bindingHandlers.num = {
      init: function (element, valueAccessor) {
        $(element).on("keypress", function (event) {
          //debugger
          console.log(event.keyCode);
          var $this = $(this);
          var text = $this.val();

          // Stop insert two dots
          if ($this.val().indexOf('.') != -1 && (event.which == 190 || event.which == 110)) {
            event.preventDefault();
          }

          // Allow: backspace, delete, tab, escape, and enter
          if (event.keyCode == 46 || event.keyCode == 8 || event.keyCode == 9 || event.keyCode == 27 || event.keyCode ==
            13 ||
            // Allow: Ctrl+A
            (event.keyCode == 65 && event.ctrlKey === true) ||
            // Allow: .   ,event.keyCode == 188 ||
            ( event.keyCode == 190 || event.keyCode == 110) ||
            // Allow: home, end, left, right
            (event.keyCode >= 35 && event.keyCode <= 39)) {
            // let it happen, don't do anything
            return;
          }

          // Ensure that it is a number and stop the keypress
          if (event.shiftKey || (event.keyCode < 48 || event.keyCode > 57) && (event.keyCode < 96 || event.keyCode >
              105)) {
            event.preventDefault();
          }

          if ((event.which == 46) && (text.indexOf('.') == -1)) {
            setTimeout(function () {
              if ($this.val().substring($this.val().indexOf('.')).length > 3) {
                $this.val($this.val().substring(0, $this.val().indexOf('.') + 3));
              }
            }, 1);
          }

          if ((text.indexOf('.') != -1) &&
            (text.substring(text.indexOf('.')).length > 2) &&
            (event.which != 0 && event.which != 8) &&
            ($(this)[0].selectionStart >= text.length - 2)) {
            event.preventDefault();
          }          
          //console.log($(this)[0].selectionStart >= text.length - 2);
        });
      }
    };


    ko.extenders.numeric = function (target, precision) {
      //create a writable computed observable to intercept writes to our observable

      var result = ko.pureComputed({
        read: target, //always return the original observables value
        write: function (newValue) {

          var current = target(),
            roundingMultiplier = Math.pow(10, precision),
            newValueAsNum = isNaN(newValue) ? 0 : parseFloat(+newValue),
            valueToWrite = Math.round(newValueAsNum * roundingMultiplier) / roundingMultiplier;

          //only write if it changed
          if (valueToWrite !== current) {
            target(valueToWrite);
          } else {
            //if the rounded value is the same, but a different value was written, force a notification for the current field
            if (newValue !== current) {
              target.notifySubscribers(valueToWrite);
            }
          }
        }
      }).extend({
        notify: 'always'
      });

      //initialize with current value to make sure it is rounded appropriately
      result(target());

      //return the new computed observable
      return result;
    };

    function AppViewModel(one, two) {
      this.myNumberOne = ko.observable(one).extend({
        numeric: 0
      });
      this.myNumberTwo = ko.observable(two).extend({
        numeric: 2
      });
    }

    ko.applyBindings(new AppViewModel(221.2234, 123.4525));
  </script>