Using pre-compiled templates with Handlebars.js (jQuery Mobile environment)

Question

I am struggling somewhat with pre-compilation of templates in Handlebars. My jQuery Mobile project is getting pretty big template-wise and I wish to pre-compile the template

Answer 1

Another great option for this is to use GruntJS. Once installed:

npm install grunt-contrib-handlebars --save-dev

Then inside your gruntfile.js

grunt.initConfig({
    dirs: {
      handlebars: 'app/handlebars'
    },
    watch: {
      handlebars: {
        files: ['<%= handlebars.compile.src %>'],
        tasks: ['handlebars:compile']
      }
    },
    handlebars: {
      compile: {
        src: '<%= dirs.handlebars %>/*.handlebars',
        dest: '<%= dirs.handlebars %>/handlebars-templates.js'
      }
    }
});


grunt.loadNpmTasks('grunt-contrib-handlebars');

Then you simply type grunt watch from your console, and grunt will automatically compile all *.handlebars files into your handlebars-templates.js file.

Really rad way to work with handlebars.

Answer 2

For Handlebars 2.0.0 alpha Update:

@Macro has explained quite clearly how it works with 1 piece of template, please see this answer for how to make handlebars.js works

If you see "TypeError: 'undefined' is not a function" when using precompiled templates:

This error happened at "handlebar.runtime.js" line 436 when evaluting templateSpec.call(container, Handlebars, context, options.helpers, options.partials, options.data),

because the compiler npm installed is not matching the one used by the browser. The latest stable version downloaded is v1.3.0 while if you use npm install handlebars, it will install 2.0.0-alpha4 for you.

Please check it out using

handlebars any_your_template_before_compile.handlebars | grep "compiler"

which will give you like, if you indeed installed handlebar 2.0.0-alpha4:

this.compiler = [5, '>=2.0.0']

With the first number stands for the version for your handlebar compiler. Type in the following code in browser console, see if the result match the version.

Handlebars.COMPILER_REVISION

If you have compiler 5 with browser revison 4, then you will have the above problem.

To fix it, install handlebar 1.3.0 with the following command

npm install handlebars@1.3.0 -g

Then try to compile it again, you will see this time, it gives you matching version info and you are good to go with the precompiled templates.

this.compilerInfo = [4, '>=1.0.0']

Just explain if you have tons of templates:

Firstly externalize each piece of your braced templates: event.handlebars, item.handlebars, etc... You can put them all in one folder, say "/templates"

Compile all the files and concatenate it into 1 file with the following command:

handlebars *.handlebars -f templates.js

And include handlebars.runtime, this file in your HTML

<script src="/lib/handlebars.runtime.js"></script>
<script src="templates.js"></script>

The templates will be injected into Handlebars.templates by their name. For example, event.handlebars can be accessed by Handlebars.tempaltes['event'].

Answer 3

Here is the way I do it:

Preparation

We will just assume all your template variables are in a variable called context:

var context = {
    name: "Test Person",
    ...
};

Where to put your templates

Create a directory containing all your templates (we'll call it templates/) Add your templates here, called filename.handlebars.

Your directory structure:

.
└── templates
    ├── another_template.handlebars
    └── my_template.handelbars

Compiling your templates

First go to your root directory, then compile your templates with the npm CLI program:

handlebars templates/*.handlebars -f compiled.js

New directory structure:

.
├── compiled.js
└── templates
    ├── another_template.handlebars
    └── my_template.handlebars

Usage

Include the compiled.js in your HTML page after you include the runtime:

<script src="handlebars.runtime.js"></script>
<script src="compiled.js"></script>

Render your templates using the global Handlebars object:

// If you used JavaScript object property conform file names
// Original filename: "my_template.handlebars"
Handlebars.templates.my_template(context)

// if you used special characters which are not allowed in JavaScript properties
// Original filename: "my-template.handlebars"
Handlebars.templates["my-template"](context)

Remarks

Note the file extension .handlebars. It is automatically stripped when compiling the templates.

Extra: if you use one of the Jetbrains IDEs together with the Handlebars/Mustache plugin you even get quite a good editor support.

Answer 4

Precompiling Handlebars Templates with Grunt

Assuming you have Node.js installed. If you don't, go do that.

1) Setting up Node dependencies:

In your applications root directory add a file named package.json. Paste the following into that file:

{
  "devDependencies": {
   "grunt-contrib-handlebars": "~0.6.0",
    "grunt-contrib-watch": "~0.5.3",
    "handlebars": "~1.3.0"
  },
}

This JSON file tells Node what packages it needs to install. This helps to get other developers get up-and-running very quickly, as you'll see in the next step.

2) Installing Node Dependencies:

In your terminal/command prompt/powershell, cd into your projects root directory and run the following commands:

npm install grunt -g
npm install grunt-cli -g

And to install the dependencies listed in your package.json:

npm install

Now you've installed all of the node dependencies that you need. In your projects root directory, you'll see a node_modules folder.

3) Configuring Grunt:

In your projects root directory, create a file named Gruntfile.js. Paste the following into that file:

module.exports = function(grunt) {

    var TEMPLATES_LOCATION        = "./src/templates/",       // don't forget the trailing /
        TEMPLATES_EXTENSION       = ".hbs",
        TEMPLATES_OUTPUT_LOCATION = TEMPLATES_LOCATION,       // don't forget the trailing /
        TEMPLATES_OUTPUT_FILENAME = "compiled_templates.js";  // don't forget the .js

    grunt.initConfig({
        watch: {
            handlebars: {
                files: [TEMPLATES_LOCATION + '**/*' + TEMPLATES_EXTENSION],
                tasks: ['handlebars:compile']
            }
        },
        handlebars: {
            compile: {
                src: TEMPLATES_LOCATION + '**/*' + TEMPLATES_EXTENSION,
                dest: TEMPLATES_OUTPUT_LOCATION + TEMPLATES_OUTPUT_FILENAME,
                options: {
                    amd: true,
                    namespace: "templates"
                }
            }
        }
    });

    grunt.loadNpmTasks('grunt-contrib-handlebars');
    grunt.loadNpmTasks('grunt-contrib-watch');

}

4) Configuring to Your Liking:

If you are not using Require.js, you'll want to change handlebars.compile.options.amd to false. You may also want to tweak the namespace option to your liking. If you're using require/amd modules, the namespace property is unimportant (it's default is "JST", if you remove it).

Because all project structures are a little bit different, you'll need to configure the Gruntfile just a little bit. Modify the constants TEMPLATES_LOCATION, TEMPLATES_EXTENSION, TEMPLATES_OUTPUT_LOCATION, TEMPLATES_OUTPUT_FILENAME to fit your project.

If your templates are scattered throughout your application, you'll want to change TEMPLATES_LOCATION to the lowest directory possible. Make sure your templates are isolated from your node_modules, bower_components or any other 3rd party directories, because you don't want Grunt to compile 3rd Party templates into your applications compiled templates. If you include all of your own code in a ./src, ./js, ./app directory, you'll be okay.

5) Compiling templates with Grunt:

To run grunt in the background, open your terminal and cd into your projects root directory and run the command: grunt watch:handlebars (just grunt watch works as well). With grunt running in the background, all changes to your template files will be automatically compiled and the output file specified handlebars.compile.dest will be rewritten as needed. The output will look something like this:

Running "watch" task
Waiting...

To run the compile task alone, open your terminal and cd into your projects root directory and run the command: grunt handlebars:compile (just grunt:handlebars works as well). The output will look something like:

Running "handlebars:compile" <handlebars> task
File "./src/templates/compiled_templates.js" created.

Done, without errors.

Answer 5

So after much trial and error (which is the best way to learn it) here's the way that works for me.

First- externalize all your templates, say you have a template inside script tags like

<script id="tmpl_ownevents" type="text/templates">
    {{#unless event}}
        <div class="notfoundevents"><p>No events for you</p></div>    
    {{/unless}}
</script>

Create a new file called events.tmpl and copy/paste the template into that. Be sure to remove the script elements themselves, this gotcha bit me in the a..

Install the Handlebars commandline script like so

npm install -g handlebars

go to the folder you have saved events.tmpl into and run

handlebars events.tmpl -f events.tmpl.js

Include the compiled javascript into your HTML after you included Handlebars.js

<script src="events.tmpl.js"></script>

Now all that is left is change your normal template code into something resembling the following

var template = Handlebars.templates['events.tmpl'], // your template minus the .js
    context = events.all(), // your data
    html    = template(context);

And there you have it, super fast pre-compiled Handlebars templates.