3.20.0 • Public • Published

JavaScript Templates



1KB lightweight, fast & powerful JavaScript templating engine with zero dependencies.
Compatible with server-side environments like Node.js, module loaders like RequireJS or webpack and all web browsers.



Install the blueimp-tmpl package with NPM:

npm install blueimp-tmpl

Include the (minified) JavaScript Templates script in your HTML markup:

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

Add a script section with type "text/x-tmpl", a unique id property and your template definition as content:

<script type="text/x-tmpl" id="tmpl-demo">
  <p>Released under the
  <a href="{%=o.license.url%}">{}</a>.</p>
  {% for (var i=0; i<o.features.length; i++) { %}
  {% } %}

"o" (the lowercase letter) is a reference to the data parameter of the template function (see the API section on how to modify this identifier).

In your application code, create a JavaScript object to use as data for the template:

var data = {
  title: 'JavaScript Templates',
  license: {
    name: 'MIT license',
    url: ''
  features: ['lightweight & fast', 'powerful', 'zero dependencies']

In a real application, this data could be the result of retrieving a JSON resource.

Render the result by calling the tmpl() method with the id of the template and the data object as arguments:

document.getElementById('result').innerHTML = tmpl('tmpl-demo', data)


The following is an example how to use the JavaScript Templates engine on the server-side with Node.js.

Install the blueimp-tmpl package with NPM:

npm install blueimp-tmpl

Add a file template.html with the following content:

<h3><a href="{%=o.url%}">{%=o.title%}</a></h3>
{% for (var i=0; i<o.features.length; i++) { %}
{% } %}

Add a file server.js with the following content:

  .createServer(function (req, res) {
    var fs = require('fs'),
      // The tmpl module exports the tmpl() function:
      tmpl = require('./tmpl'),
      // Use the following version if you installed the package with npm:
      // tmpl = require("blueimp-tmpl"),
      // Sample data:
      data = {
        title: 'JavaScript Templates',
        url: '',
        features: ['lightweight & fast', 'powerful', 'zero dependencies']
    // Override the template loading method:
    tmpl.load = function (id) {
      var filename = id + '.html'
      console.log('Loading ' + filename)
      return fs.readFileSync(filename, 'utf8')
    res.writeHead(200, { 'Content-Type': 'text/x-tmpl' })
    // Render the content:
    res.end(tmpl('template', data))
  .listen(8080, 'localhost')
console.log('Server running at http://localhost:8080/')

Run the application with the following command:

node server.js


The JavaScript Templates script has zero dependencies.


tmpl() function

The tmpl() function is added to the global window object and can be called as global function:

var result = tmpl('tmpl-demo', data)

The tmpl() function can be called with the id of a template, or with a template string:

var result = tmpl('<h3>{%=o.title%}</h3>', data)

If called without second argument, tmpl() returns a reusable template function:

var func = tmpl('<h3>{%=o.title%}</h3>')
document.getElementById('result').innerHTML = func(data)

Templates cache

Templates loaded by id are cached in the map tmpl.cache:

var func = tmpl('tmpl-demo'), // Loads and parses the template
  cached = typeof tmpl.cache['tmpl-demo'] === 'function', // true
  result = tmpl('tmpl-demo', data) // Uses cached template function

tmpl.cache['tmpl-demo'] = null
result = tmpl('tmpl-demo', data) // Loads and parses the template again

Output encoding

The method tmpl.encode is used to escape HTML special characters in the template output:

var output = tmpl.encode('<>&"\'\x00') // Renders "&lt;&gt;&amp;&quot;&#39;"

tmpl.encode makes use of the regular expression tmpl.encReg and the encoding map tmpl.encMap to match and replace special characters, which can be modified to change the behavior of the output encoding.
Strings matched by the regular expression, but not found in the encoding map are removed from the output. This allows for example to automatically trim input values (removing whitespace from the start and end of the string):

tmpl.encReg = /(^\s+)|(\s+$)|[<>&"'\x00]/g
var output = tmpl.encode('    Banana!    ') // Renders "Banana" (without whitespace)

Local helper variables

The local variables available inside the templates are the following:

  • o: The data object given as parameter to the template function (see the next section on how to modify the parameter name).
  • tmpl: A reference to the tmpl function object.
  • _s: The string for the rendered result content.
  • _e: A reference to the tmpl.encode method.
  • print: Helper function to add content to the rendered result string.
  • include: Helper function to include the return value of a different template in the result.

To introduce additional local helper variables, the string tmpl.helper can be extended. The following adds a convenience function for console.log and a streaming function, that streams the template rendering result back to the callback argument (note the comma at the beginning of each variable declaration):

tmpl.helper +=
  ',log=function(){console.log.apply(console, arguments)}' +
  ",st='',stream=function(cb){var l=st.length;st=_s;cb( _s.slice(l));}"

Those new helper functions could be used to stream the template contents to the console output:

<script type="text/x-tmpl" id="tmpl-demo">
  {% stream(log); %}
  <p>Released under the
  <a href="{%=o.license.url%}">{}</a>.</p>
  {% stream(log); %}
  {% stream(log); %}
  {% for (var i=0; i<o.features.length; i++) { %}
      {% stream(log); %}
  {% } %}
  {% stream(log); %}

Template function argument

The generated template functions accept one argument, which is the data object given to the tmpl(id, data) function. This argument is available inside the template definitions as parameter o (the lowercase letter).

The argument name can be modified by overriding tmpl.arg:

tmpl.arg = 'p'

// Renders "<h3>JavaScript Templates</h3>":
var result = tmpl('<h3>{%=p.title%}</h3>', { title: 'JavaScript Templates' })

Template parsing

The template contents are matched and replaced using the regular expression tmpl.regexp and the replacement function tmpl.func. The replacement function operates based on the parenthesized submatch strings.

To use different tags for the template syntax, override tmpl.regexp with a modified regular expression, by exchanging all occurrences of "{%" and "%}", e.g. with "[%" and "%]":

tmpl.regexp = /([\s'\\])(?!(?:[^[]|\[(?!%))*%\])|(?:\[%(=|#)([\s\S]+?)%\])|(\[%)|(%\])/g

By default, the plugin preserves whitespace (newlines, carriage returns, tabs and spaces). To strip unnecessary whitespace, you can override the tmpl.func function, e.g. with the following code:

var originalFunc = tmpl.func
tmpl.func = function (s, p1, p2, p3, p4, p5, offset, str) {
  if (p1 && /\s/.test(p1)) {
    if (
      !offset ||
      /\s/.test(str.charAt(offset - 1)) ||
    ) {
      return ''
    return ' '
  return originalFunc.apply(tmpl, arguments)

Templates syntax


Print variable with HTML special characters escaped:


Print variable without escaping:


Print output of function calls:

<a href="{%=encodeURI(o.url)%}">Website</a>

Use dot notation to print nested properties:



Use print(str) to add escaped content to the output:

<span>Year: {% var d=new Date(); print(d.getFullYear()); %}</span>

Use print(str, true) to add unescaped content to the output:

<span>{% print("Fast &amp; powerful", true); %}</span>

Use include(str, obj) to include content from a different template:

  {% include('tmpl-link', {name: "Website", url: ""}); %}

If else condition:

{% if ( { %}
<a href="{%=encodeURI(}">{}</a>
{% } else { %}
<em>No author url.</em>
{% } %}

For loop:

{% for (var i=0; i<o.features.length; i++) { %}
{% } %}

Compiled templates

The JavaScript Templates project comes with a compilation script, that allows you to compile your templates into JavaScript code and combine them with a minimal Templates runtime into one combined JavaScript file.

The compilation script is built for Node.js.
To use it, first install the JavaScript Templates project via NPM:

npm install blueimp-tmpl

This will put the executable tmpl.js into the folder node_modules/.bin. It will also make it available on your PATH if you install the package globally (by adding the -g flag to the install command).

The tmpl.js executable accepts the paths to one or multiple template files as command line arguments and prints the generated JavaScript code to the console output. The following command line shows you how to store the generated code in a new JavaScript file that can be included in your project:

tmpl.js index.html > tmpl.js

The files given as command line arguments to tmpl.js can either be pure template files or HTML documents with embedded template script sections. For the pure template files, the file names (without extension) serve as template ids.
The generated file can be included in your project as a replacement for the original tmpl.js runtime. It provides you with the same API and provides a tmpl(id, data) function that accepts the id of one of your templates as first and a data object as optional second parameter.


The JavaScript Templates project comes with Unit Tests.
There are two different ways to run the tests:

  • Open test/index.html in your browser or
  • run npm test in the Terminal in the root path of the repository package.

The first one tests the browser integration, the second one the Node.js integration.


The JavaScript Templates script is released under the MIT license.

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