shiny/srcjs/input_binding_number.js

var numberInputBinding = {};
$.extend(numberInputBinding, textInputBinding, {
  find: function(scope) {
    return $(scope).find('input[type="number"]');
  },
  getValue: function(el) {
    var numberVal = $(el).val();
    if (/^\s*$/.test(numberVal))  // Return null if all whitespace
      return null;
    else if (!isNaN(numberVal))   // If valid Javascript number string, coerce to number
      return +numberVal;
    else
      return numberVal;           // If other string like "1e6", send it unchanged
  },
  setValue: function(el, value) {
    el.value = value;
  },
  getType: function(el) {
    return "shiny.number";
  },
  receiveMessage: function(el, data) {
    if (data.hasOwnProperty('value'))  el.value = data.value;
    if (data.hasOwnProperty('min'))    el.min   = data.min;
    if (data.hasOwnProperty('max'))    el.max   = data.max;
    if (data.hasOwnProperty('step'))   el.step  = data.step;

    if (data.hasOwnProperty('label'))
      $(el).parent().find('label[for="' + $escape(el.id) + '"]').text(data.label);

    $(el).trigger('change');
  },
  getState: function(el) {
    return { label: $(el).parent().find('label[for="' + $escape(el.id) + '"]').text(),
             value: this.getValue(el),
             min:   Number(el.min),
             max:   Number(el.max),
             step:  Number(el.step) };
  }
});
inputBindings.register(numberInputBinding, 'shiny.numberInput');