Pug call js function from another file inside template

Question

I can't solve this for almost four hours, and i can't find any helpful documentation for this kind of problems. This is the issue, I'm using pug/jade templates and i want to call function inside pug template to transform some data This is the main template:

 /** main template */
section
  each pet in pets
    .pet
      .photo-column
        img(src= pet.photo)
      .info-column  
        h2= pet.name 
        span.species= (pet.species)
        p Age: #{calculateAge(pet.birthYear)} //here I need to call calculateAge function
        if pet.favFoods
          h4.headline-bar Favorite Foods
          ul.favorite-foods
            each favFood in pet.favFoods
              li!= favFood
/** end main template **/

This is the external function:

/** calculateAge.js **/

 module.exports = function(birthYear) {
   var age = new Date().getFullYear() - birthYear;

   if (age > 0) {
     return age + " years old";
   } else {
     return "Less than a year old";
   }
 };
/** end calculateAge.js **/

What shell I do to make this happen?

Answer 1

There may be better way to handle this, but I usually do it by importing the external module and then passing it as part of template context object. That means the code that renders the template should be something like:

const calculateAge = require("calculateAge"); // change path accordingly

router.get("/main", function(){
  let pageInfo = {};
  pageInfo.title = "Demo";
  pageInfo.calculateAge = calculateAge;
  res.render("main", pageInfo);
});

Now, you can access calculateAge in your template. If this module is used a lot in most of the templates, then you should pass it as part of res.locals or app.locals so that it is available for all templates without the need to append it for every path request.

Answer 2

In PUG options use locals property to import functions you want to use inside your templates.

const calculateAge = require('./calculate-age');

const config = {
  pug: {
    locals: {
      calculateAge,
    },
  },
};

Then you can use it in all your templates like this (please note the extra unescaping tag !{}):

p Age: !{calculateAge(pet.birthYear)}