function isValueNumber(value) {
 return (/(^-?[0-9]+\.{1}\d+$) | (^-?[1-9][0-9]*$) | (^-?0{1}$)/).test(value + '');
}


Vue.component('input-number',{
 template: '\
  
\
   \
   -\
   +\
  
',
 props: {
  max: {
   type: Number,
   default: Infinity
  },
  min: {
   type: Number,
   default: -Infinity
  },
  value: {
   type: Number,
   default: 0
  }
 },
 data: function () {
  return {
   currentValue: this.value
  }
 },
 watch: {
  currentValue: function (val) {
   this.$emit('input', val);
   this.$emit('on-change',val);
  },
  value: function (val) {
   this.updateValue(val);
  }
 },
 methods: {
  updateValue: function (val) {
   if(val > this.max)
    val = this.max;
   if(val < this.min)
    val = this.min;
   this.currentValue = val;
  },
  handleDown: function () {
   if(this.currentVaule <= this.min)
    return;
   this.currentValue -= 1;
  },
  handleUp: function () {
   if(this.currentVaule >= this.max)
    return;
   this.currentValue += 1;
  },
  handleChange: function (event) {
   var val = event.target.value.trim();

   var max = this.max;
   var min = this.min;

   if(isValueNumber(val)){
    val = Number(val);
    this.currentValue = val;

    if(val > max){
     this.currentValue = max;
    }else if(val < min){
     this.currentValue = min;
    }
   }else{
    event.target.value = this.currentValue;
   }
  }
 },
 mounted: function () {
  this.updateValue(this.value);
 }
});

var app = new Vue({
 el: '#app',
 data: {
  value: 5
 }
});