mustache.js date formatting

Question

I have started using mustache.js and so far I am very impressed. Although two things puzzle me. The first leads on to the second so bear with me.

My JSON

{"goalsCollection": [
    {
        "Id": "d5dce10e-513c-449d-8e34-8fe771fa464a",
        "Description": "Multum",
        "TargetAmount": 2935.9,
        "TargetDate": "/Date(1558998000000)/"
    },
    {
        "Id": "eac65501-21f5-f831-fb07-dcfead50d1d9",
        "Description": "quad nomen",
        "TargetAmount": 6976.12,
        "TargetDate": "/Date(1606953600000)/"
    }
]};

My handling function

function renderInvestmentGoals(collection) {
    var tpl = '{{#goalsCollection}}<tr><td>{{Description}}</td><td>{{TargetAmount}}</td><td>{{TargetDate}}</td></tr>{{/goalsCollection}}';
    $('#tblGoals tbody').html('').html(Mustache.to_html(tpl, collection));
}

Q1 As you can see my 'TargetDate' needs parsing but I am unsure of how to do that within my current function.

Q2 Say I wanted to perform some function or formatting on one or more of my objects before rendering, what is the best way of doing it?

Answer 1

You can use "Lambdas" from mustache(5)

"TargetDate": "/Date(1606953600000)/",
"FormatDate": function() {
    return function(rawDate) {
        return rawDate.toString();
    }
}, ...

Then in the markup:

<td>
{{#FormatDate}}
    {{TargetDate}}
{{/FormatDate}}
</td>

From the link:

When the value is a callable object, such as a function or lambda, the object will be invoked and passed the block of text. The text passed is the literal block, unrendered.

Answer 2

I have created a small extension for Mustache.js which enables the use of formatters inside of expressions, like {{expression | formatter}}

You would anyway need to create a function that parses your date value like this:

      Mustache.Formatters = {
        date: function( str) {
          var dt = new Date( parseInt( str.substr(6, str.length-8), 10));
          return (dt.getDate() + "/" + (dt.getMonth() + 1) + "/" + dt.getFullYear());
        }
      };

And then just add the formatter to your expressions:

{{TargetDate | date}}

You can grab the code from here: http://jvitela.github.io/mustache-wax/

Answer 3

It's a long time ago but got on this looking for exactly the same. Mustachejs (now) allows you to call functions of the passed data and not only that; in the function the value of this is whatever value is true in a section.

If my template is like this:

{{#names}}
    <p>Name is:{{name}}</p>
    <!-- Comment will be removed by compileTemplates.sh
         #lastLogin is an if statement if lastLogin it'll do this 
         ^lastLogin will execute if there is not lastLogin      
    -->
    {{#lastLogin}}
    <!-- 
      formatLogin is a method to format last Login 
      the function has to be part of the data sent 
      to the template
    -->
    <p>Last Login:{{formatLogin}}</p>
    {{/lastLogin}}
    {{^lastLogin}}
    not logged in yet
    {{/lastLogin}}
    {{#name}}
     passing name to it now:{{formatLogin}}
    {{/name}}
{{/names}}

And Data like this:

var data={
    names:[
        {name:"Willy",lastLogin:new Date()}
    ],
    formatLogin:function(){
          //this is the lastDate used or name based on the block
                  //{{#name}}{{formatLogin}}{{/name}}:this is name
                  //{{#lastLogin}}{{formatLogin}}{{/lastLogin}}:this is lastLogin
          if(!/Date\]$/.test(Object.prototype.toString.call(this))){
              return "Invalid Date:"+this;
          }
          return this.getFullYear()
            +"-"+this.getMonth()+1
            +"-"+this.getDate();
    }
};
var output = Mustache.render(templates.test, data);
console.log(output);

Answer 4

You can get the timestamp using simple String methods:

goalsCollection.targetDate = goalsCollection.targetDate.substring(6,18);

Of course, this depends on your timestamp being the same length each time. Another option is:

goalsCollection.targetDate = 
  goalsCollection.targetDate.substring(6, goalsCollection.targetDate.length - 1);

These techniques aren't specific to Mustache and can be used to manipulate data for any library. See the Mozilla Developer Center Documentation on substring for more details.

Answer 5

To declare a function within a json you can always do this.

var json = '{"RESULTS": true, "count": 1, "targetdate" : "/Date(1606953600000)/"}'

var obj = JSON.parse(json);
obj.newFunc = function (x) {
  return x;
}

//OUTPUT
alert(obj.newFunc(123));

Answer 6

Working example of a 'lambda' function for parsing an ISO-8601 date and formatting as UTC:

var data = [
  {
    "name": "Start",
    "date": "2020-04-11T00:32:00.000-04:00"
  },
  {
    "name": "End",
    "date": "2022-04-11T00:32:00.000-04:00"
  },
]

var template = `
{{#items}}
<h1>{{name}}</h1>
  {{#dateFormat}}
     {{date}}
  {{/dateFormat}}
{{/items}}
`;


var html = Mustache.render(template, {
  items: data,
  dateFormat: function () {
    return function (timestamp, render) {
      return new Date(render(timestamp).trim()).toUTCString();
    };
  }
});

document.getElementById("main").innerHTML = html;

<script src="https://unpkg.com/mustache@4.2.0/mustache.min.js"></script>

<div id="main"></div>

If you want fancier date formatting you could use for example something like:

new Date().toLocaleDateString('en-GB', {
    day : 'numeric',
    month : 'short',
    year : 'numeric', hour: 'numeric', minute: 'numeric'
})
// outputs '14 Apr 2022, 11:11'

Answer 7

I've been using Mustache for my projects as well, due to its ability to be shared across client/server. What I ended up doing was formatting all values (dates, currency) to strings server-side, so I don't have to rely on helper Javascript functions. This may not work well for you though, if you're doing logic against these values client-side.

You might also want to look into using handlebars.js, which is essentially Mustache, but with extensions that may help with client-side formatting (and more). The loss here is that you will probably not be able to find a server-side implementation of handlebars, if that matters to you.