# JavaScript Templates
## Demo
[JavaScript Templates Demo](http://blueimp.github.com/JavaScript-Templates/)
## Usage
### Client-side
Include the (minified) JavaScript Templates script in your HTML markup:
```html
```
Add a script section with type **"text/html"** and your template definition as content:
```html
```
**"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:
```js
var data = {
"title": "JavaScript Templates",
"license": {
"name": "MIT license",
"url": "http://www.opensource.org/licenses/MIT"
},
"features": [
"lightweight & fast",
"powerful",
"zero dependencies"
]
};
```
In a real application, this data could be the result of retrieving a [JSON](http://json.org/) resource.
Render the result by calling the **tmpl()** method with the id of the template and the data object as arguments:
```js
document.getElementById("result").innerHTML = tmpl("tmpl-demo", data);
```
### Server-side
The following is an example how to use the JavaScript Templates engine on the server-side with [node.js](http://nodejs.org/).
Create a new directory and add the **tmpl.js** file. Or alternatively, install the **blueimp-tmpl** package with [npm](http://npmjs.org/):
```sh
npm install blueimp-tmpl
```
Add a file **template.html** with the following content:
```html
{%=o.title%}
Features
{% for (var i=0; i{%=o.features[i]%}
{% } %}
```
Add a file **server.js** with the following content:
```js
require("http").createServer(function (req, res) {
var fs = require("fs"),
// The tmpl module exports the tmpl() function:
tmpl = require("./tmpl").tmpl,
// Use the following version if you installed the package with npm:
// tmpl = require("blueimp-tmpl").tmpl,
// Sample data:
data = {
"title": "JavaScript Templates",
"url": "https://github.com/blueimp/JavaScript-Templates",
"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/html"});
// 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:
```sh
node server.js
```
## Requirements
The JavaScript Templates script has zero dependencies.
## API
### tmpl() function
The **tmpl()** function is added to the global **window** object and can be called as global function:
```js
var result = tmpl("tmpl-demo", data);
```
The **tmpl()** function can be called with the id of a template, or with a template string:
```js
var result = tmpl("{%=o.title%}
", data);
```
If called without second argument, **tmpl()** returns a reusable template function:
```js
var func = tmpl("{%=o.title%}
");
document.getElementById("result").innerHTML = func(data);
```
### Templates cache
Templates loaded by id are cached in the map **tmpl.cache**, which can be modified:
```js
var func = tmpl("tmpl-demo");
var cached = typeof tmpl.cache["tmpl-demo"] === "function"; // true
tmpl.cache["tmpl-demo"] = tmpl("{%=o.title%}
");
var result = tmpl("tmpl-demo", {title: "JS"}); // Renders "JS
"
```
### Output encoding
The method **tmpl.encode** is used to escape HTML special characters in template output:
```js
var output = tmpl.encode("<>&\"\x00"); // Renders "<>&""
```
**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:
```js
// Add single quotes to the encoding rules:
tmpl.encReg = /[<>&"'\x00]/g;
tmpl.encMap["'"] = "'";
var output = tmpl.encode("<>&\"'\x00"); // Renders "<>&"'"
```
### 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).
* **_s**: The string for the rendered result content.
* **_t**: A reference to the **tmpl** function object.
* **_e**: A reference to the **tmpl.encode** method.
* **print**: Function to add content to the rendered result string.
* **include**: 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):
```js
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:
```html
```
### 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**:
```js
tmpl.arg = "p";
// Renders "JavaScript Templates
":
var result = tmpl("{%=p.title%}
", {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](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String/replace#Specifying_a_function_as_a_parameter).
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 "**%\\]**":
```js
tmpl.regexp = /(\s+)|('|\\)(?![^%]*%\])|(?:\[%(=|#)(.+?)%\])|(\[%)|(%\])/g;
```
## Templates syntax
### Interpolation
Print variable with HTML special characters escaped:
```html
{%=o.title%}
```
Print variable without escaping:
```html
{%#o.user_id%}
```
Print output of function calls:
```html
Website
```
Use dot notation to print nested properties:
```html
{%=o.author.name%}
```
Note that the JavaScript Templates engine prints **falsy** values as empty strings.
That is, **undefined**, **null**, **false**, **0** and **NaN** will all be converted to **''**.
To be able to print e.g. the number 0, convert it to a String before using it as an output variable:
```html
{%=0+''%}
```
### Evaluation
Use **print(str)** to add escaped content to the output:
```html
Year: {% var d=new Date(); print(d.getFullYear()); %}
```
Use **print(str, true)** to add unescaped content to the output:
```html
{% print("Fast & powerful", true); %}
```
Use **include(str, obj)** to include content from a different template:
```html
{% include('tmpl-link', {name: "Website", url: "http://example.org"}); %}
```
If else condition:
```html
{% if (o.author.url) { %}
{%=o.author.name%}
{% } else { %}
No author url.
{% } %}
```
For loop:
```html
{% for (var i=0; i{%=o.features[i]%}
{% } %}
```
## License
The JavaScript Templates script is released under the [MIT license](http://www.opensource.org/licenses/MIT).