jsTACS

JavaScript Templating and Caching System for Node.js.

This is a beta product primary designed for the Publican static site generator. Please use at your own discretion.

jsTACs uses tagged template literals for zero-dependency fast template rendering. Features:

• ECMAScript module
• standard JavaScript template literal ${ expression }
• !{ expression } is ignored in the initial render so it can be evaluated at runtime. It's possible to pre-build templates so only runtime data remains.
• include other files
• pass global data and custom functions.

Basic usage

Replace expressions in a template string:

import { templateParse } from 'jstacs';

/*
output:
<p>Hello World!</p>
*/
const out1a = templateParse(
  '<p>Hello ${ data.name }!</p>',
  { name: 'World' }
);


/*
output:
<p>Hello World!</p>
*/
const out1b = templateParse(
  '${ data.name && `<p>Hello ${ data.name }!</p>` }',
  { name: 'World' }
);

/*
output: blank
*/
const out1c = templateParse(
  '${ data.name && `<p>Hello ${ data.name }!</p>` }',
  { name: null }
);

data properties such as data.name typically hold a string, number, or another native value. null, undefined, and NaN return an empty string, but true, false, and 0 are rendered as text. Arrays, Sets, and Maps are automatically output: there's no need for .join('') unless you want a specific character between each value.

/*
output:
<ol><li>1</li><li>2</li><li>3</li></ol>
*/
const out2 = templateParse(
  '<ol>${ data.list.map(i => `<li>${ i }</li>`) }</ol>',
  { list: [1, 2, 3] }
);

Use !{ expression } to return a partially-completed template which can be saved and used later:

/*
output:
<p>Hello World! The time is ${ data.now }</p>
*/
const out3 = templateParse(
  '<p>Hello ${ data.name }! The time is !{ data.now }.</p>',
  { name: 'World' }
);

Convert any value to an array

Any object, Map, Set, or value can be converted to an array using toArray() for easier output:

/*
output:
<p>a, b, c</p>
*/
const out4 = templateParse(
  '<p>${ toArray(data.set).join(', ') }</p>',
  { set: new Set(['a', 'b', 'c']) }
);

File includes

A template can include another with include(filename):

const out5 = templateParse(
  '${ include("./template/index.html") }',
  {}
);

Files can be fully-qualified or relative to the project root directory. You can also set a template directory in the tacsConfig configuration object. All includes and sub-includes use this directory:

import { tacsConfig, templateParse } from 'jstacs';

tacsConfig.dir.template = './template/';

const out6 = templateParse(
  '${ include("index.html") }',
  {}
);

Global values

Global values and functions can be passed to a template using the tacs object.

import { tacs, templateParse } from 'jstacs';

tacs.global = tacs.global || {};
tacs.global.list = ['a', 'b', 'c'];

tacs.exec = tacs.exec || {};
tacs.exec.olList = list => '<ol>' + list.map(i => `<li>${ i }</li>`).join('') + '<ol>';

/*
output:
<ol><li>1</li><li>2</li><li>3</li></ol>
<ol><li>a</li><li>b</li><li>c</li></ol>
*/
const out7 = templateParse(
  '${ tacs.exec.olList( tacs.global.list ) }\n${ tacs.exec.olList( data.list ) }\n',
  { list: [ 1, 2, 3 ] }
);

Pre-loading templates

The templateMap Map object used to cache template strings loaded from files. It can be used to pre-load templates or set (or unset) virtual files so they are available when an include() is referenced:

import { templateMap, templateParse } from 'jstacs';

templateMap.set('/home/user/project/template/index.html', '${ include("header.html") }');
templateMap.set('/home/user/project/template/header.html', '<h1>${ data.title }</h1>');

Note that the full path is required even if tacsConfig.dir.template has been set.

Alternatively, you can load and cache individual files using templateGet(), but this uses readFileSync so it will not be as effect as other methods:

import { templateGet, templateParse } from 'jstacs';

templateGet('/home/user/project/template/file.html');

Using jsTACS as a rendering engine

jsTACS can be used as an Express.js rendering engine. Ideally, templates should be pre-rendered first with !{ expressions } so only runtime values need be replaced:

import express from 'express';
import { templateEngine } from 'jstacs';

const
  app = express(),
  port = 8181;

app.engine('html', templateEngine);
app.set('views', './templates');
app.set('view engine', 'html');

// render template at ./templates/index.html
app.get('/', (req, res) => {
  res.render('index', { runtime: 'runtime message' });
});

app.listen(port, () => {
  console.log(`Express started on port ${port}`);
});

Advanced options

tacsConfig.maxIterations is set to 50 by default. This ensures no more than 50 templateParse() iterations will occur and prevents circular include() expressions or recursive expressions writing other expressions.