How to register custom Handlebars helpers?

Question

After a long search I still can't seem to find much information on where to put my custom handlebars helpers. Do I put them in a <script> in my webpage's .hbs file? Do I put them in app.js? Do I put them in the page's router?

Here's the helper I'd like to register by the way:

Handlebars.registerHelper("last", function(array) {
    return array[array.length - 1];
});

I'm assuming once I've put that code somewhere I can just use it on any page by using {{last foo}}, right?

Solution

For an example, you can see the code below:

var express = require('express');

var app = express();

var expressHbs =  require('express-handlebars');

app.engine('.hbs', expressHbs({ defaultLayout: 'layout', extname: '.hbs'}).engine)
app.set('view engine', '.hbs');

var hbs = expressHbs.create({});

// register new function
hbs.handlebars.registerHelper('increasePrice', function(price) {
  price+=10;
  return price;
})

app.get('/', (req, res) => {
  res.render('home', {
    layout: false,
    totalPrice: 300,
  });
})

app.listen(3000, () => {
  console.log('Server is up');
});

The code above only an example.

You can see an example on this site: https://codesandbox.io/s/elegant-fog-1n61o

I hope it can help you.