Vue js apply filter on v-model in an input field

Question

Hope someone can help me! I have made a directive wrapping the Jasny Bootstrap Plugin more specifically the input-mask thing and everything goes well!

Now I have made a custom filter supported by moment to format the date field!

The date format that I receive from my backend application is YYY-MM-DD and I must show on the view as DD/MM/YYYY... I've tried v-model="date | myDate" but it didn't work properly!

JS

Vue.directive('input-mask', {
  params: ['mask'],

  bind: function() {
    $(this.el).inputmask({
      mask: this.params.mask
    });

  },
});

Vue.filter('my-date', function(value, formatString) {

  if (value != undefined)
    return '';

  if (formatString != undefined)
    return moment(value).format(formatString);

  return moment(value).format('DD/MM/YYYY');

});

var vm = new Vue({
  el: 'body',
  data: {
    date: '2015-06-26',
  }
});

HTML

<label>Date</label>
<input type="text" class="form-control" v-input-mask mask="99/99/9999" v-model="date">
<p>{{ date | myDate 'dd/mm/yyyy' }}</p>

There is the JSBin if somebody's interested!

Thanks in advance!

EDIT: Explaining better what I expect =)

When the page first load the input receive the value of 2015-06-26 and I would like to show that value as DD/MM/YYYY so 26/06/2015! It works properly only after I start typing something!

Answer 1

This is how I implemented a vue filter for a v-model using the watch callback, this won't update the value on load.

Vue.filter('uppercase', function (value) {
    return value.toUpperCase();
});

The html:

<input type="text" v-model="someData">

And the watch callback:

watch:{
   someData(val) {
       this.someData = this.$options.filters.uppercase(val);
    },
}

Answer 2

When you get the value initially, adjust it to fit the input. I got it working in the ready function, but you could do this after your DB call as well:

ready: function(){    
  var year = this.date.substr(0, 4);
  var monDay = this.date.substr(5,5);
  var result = monDay + "-" + year;
  this.date = result.replace(/-/g,"/");
}

You may have to do something similar on the way back up to your database as well.

Answer 3

I had a similar problem when I wanted to uppercase an input value.

This is what I ended up doing:

// create a directive to transform the model value
Vue.directive('uppercase', {
  twoWay: true, // this transformation applies back to the vm
  bind: function () {
    this.handler = function () {
      this.set(this.el.value.toUpperCase());
    }.bind(this);
    this.el.addEventListener('input', this.handler);
  },
  unbind: function () {
    this.el.removeEventListener('input', this.handler);
  }
});

Then I can use this directive on the input field with a v-model.

<input type="text" v-model="someData" v-uppercase="someData">

Now, whenever I type into this field or change someData, the value is transformed to uppercase.

This essentially did the same thing as I hoped v-model="someData | uppercase" would do. But of course, you can't do that.

In summation: make a directive that transforms the data, not a filter.

Answer 4

I understand what you are trying to do, however, because of the two way binding when using v-model, it may be better to just format the date as you receive it from the server, and then, use it with the desired format in your front-end app ('DD/MM/YYYY').

When sending the data back to the back-end, you just format it back to the desired server format ('YYYY-MM-DD').

In your Vue app, the work flow would be something like this:

 new Vue({
    el: 'body',
    data: {
      date: null,
    },
    methods: {
        getDataFromServer: function() {
                // Ajax call to get data from server

                // Let's pretend the received date data was saved in a variable (serverDate)
                // We will hardcode it for this ex.
                var serverDate = '2015-06-26';

                // Format it and save to vue data property
                this.date = this.frontEndDateFormat(serverDate);
        },
        saveDataToServer: function() {
            // Format data first before sending it back to server
            var serverDate = this.backEndDateFormat(this.date);

            // Ajax call sending formatted data (serverDate)
        },
        frontEndDateFormat: function(date) {
            return moment(date, 'YYYY-MM-DD').format('DD/MM/YYYY');
        },
        backEndDateFormat: function(date) {
            return moment(date, 'DD/MM/YYYY').format('YYYY-MM-DD');
        }
    }
  });

This works well for me, hope it helps.

Here is a fiddle for it:

https://jsfiddle.net/crabbly/xoLwkog9/

Syntax UPDATE:

    ...
    methods: {
        getDataFromServer() {
                // Ajax call to get data from server

                // Let's pretend the received date data was saved in a variable (serverDate)
                // We will hardcode it for this ex.
                const serverDate = '2015-06-26'

                // Format it and save to vue data property
                this.date = this.frontEndDateFormat(serverDate)
        },
        saveDataToServer() {
            // Format data first before sending it back to server
            const serverDate = this.backEndDateFormat(this.date)

            // Ajax call sending formatted data (serverDate)
        },
        frontEndDateFormat(date) {
            return moment(date, 'YYYY-MM-DD').format('DD/MM/YYYY')
        },
        backEndDateFormat(date) {
            return moment(date, 'DD/MM/YYYY').format('YYYY-MM-DD')
        }
    }
  })