javascript

Velocity Template Engine for JavaScript

This is a JavaScript implementation of Apache Velocity template engine.

   

Quick Start

$ npm install --save velocity-template-engine

The module contains methods render and compile, both of which can be used as pure functions.

🎨 rendering a template

Method render combines a velocity template string (vts below for short) and a data object, returning a string.

Example:

let tmpl = 'My name is ${name}. I\'m a #if($gender == "male")boy#{else}girl#end.';
let data = {
    name: 'June',
    gender: 'female'
};
window.velocity.render(tmpl, data); // "My name is June. I'm a girl."

♻️ caching

Additionally, there is a third parameter for the render method, which is an options object.

Option Property	Meaning
tmplId	A string or function representing the uniqueness of the template. For caching. The template string would be used if it was undefined.
dataId	A function which accepts the data and returns the unique id string of the data. For caching.
noCache	Whether disable caching or not.

Example:

let tmpl = 'My name is ${name}. I\'m a #if($gender == "male")boy#{else}girl#end.';
let opts = {
    tmplId: 'user-desc',
    dataId: user => Math.floor(user.time / 1000)
};
for (let i = 0; i < 1000000; i++) {
    let data = {
        time: Date.now(),
        name: 'June',
        gender: 'female'
    };
    window.velocity.render(tmpl, data, opts);
}

Note: you must clearly know what you are doing, because the cache data's amount must be in control.

📰 compiling a template to a function

Method compile compiles a vts to a pure function or a string of pure function body (to be written into files).

Example:

let tmpl = 'My name is ${name}. I\'m a #if($gender == "male")boy#{else}girl#end.';
let render = window.velocity.compile(tmpl);

// The second argument is options, and the `raw` property indicates whether to compile the vts to a string or not.
let render_raw = window.velocity.compile(tmpl, { raw: true });

let data = {
    name: 'June',
    gender: 'female'
};

render(data); // "My name is June. I'm a girl."
(new Function(render_raw))(data); // "My name is June. I'm a girl."

Directives

Name	Usage	Example
if	Condition.	#if($a) a #elseif($b) b #else c #end
foreach	Loop.	#foreach($item in $list) $velocityCount: $item #end
set	Assign a variable, declaring it at the same time if not exist.	#set($a = 1)
define	Define a variable as a block of VTL.	#set($name = "Tom") #set($gender = "male") #define($a) $name is $gender #end $a
macro	Define a functional directive as a macro of VTL.	#macro(a $name $gender) $name is $gender #end #a("Tom" "male")

More

• velocity
• pegjs

License

MIT

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